It seems to me that the system for keeping multiple caster classes completely separate when it comes to the level of spells you can learn/prepare forecloses an obvious use case for multi-classing casters: namely when you have a "fractional caster" as your primary class and you'd like to dip into a full caster class as a way of trading away a bit of your martial side for a bit more of your magic side. As written, spending a level or two studying magic full time gives you a lot more breadth in your low level spell vocabulary, but it delays your ability to learn more advanced spells. This is true even if the full caster class uses the same spell list as your fractional class (i.e., if you are an Eldritch Knight or Arcane Trickster and dip into Wizard), which seems bizarre.
The pooled system for determining spell slots using an "effective caster level" (ECL) is really nice, and it seems like there ought to be a way to make use of that concept for spell lists as well, although it seems clear that the simplest rule along these lines: "you can learn/prepare any spell you have slots for", is overpowered and leads to ridiculous outcomes like a character with one Cleric level being able to prepare 9th level cleric spells. I propose the following compromise, which is a toned down version of a proposal from Orc Labs here, which I liked but thought was still a little too powerful.
To determine whether a character can learn/prepare a spell as part of their allotment in class X, start with the character's level in class X. Then for each other class, Y, that has that spell on their list, take the number of levels earned in class Y (no more than the number of levels in class X) and multiply that number by the ratio of caster fractions between Y and X (in other words, convert levels to a common currency), then divide by 2 and round down, and add the result (for example, if X is a 1/3 caster and Y is a full caster, multiply levels in Y by 1 / (1/3) / 2 = 3/2 and round down, adding the result to levels in X). The character can learn/prepare the spell if a single class character at the combined level could do so.
As a result, a half caster can dip into a full caster class for however many levels, and for the purposes of learning spells that both classes can cast, break even on their spell level progression pace (accelerating their spell slots and gaining some class features of the new class while giving up non-spell-related features of the original one). A 1/3 caster can actually accelerate their spell level progression, at least where shared spells are concerned, by taking at least two levels in a full caster class (two levels give the benefits of three levels in the original class, at the cost of some non-spell-related features).
How does this apply to other combinations, say a full caster taking levels in another full caster? For spells they have in common, a Wizard taking levels in Cleric, for example, will still advance the maximum level of Wizard spell they can cast, as long as a Cleric can cast it too, and at half the rate of taking additional Wizard levels. So a Wizard 10 / Cleric 10, for example, can learn spells on both lists like a level 15 Wizard or level 15 Cleric (i.e., up to level 8), but for spells on only one list, can only learn what a level 10 character could learn (i.e., up to level 5).
The choice of 2 as the number to divide "borrowed levels" by is arbitrary, and could be tweaked to make this more or less powerful (you could even use one number if the classes share a casting ability and a bigger number if not, reflecting greater or lesser similarity in the techniques used to cast the spell, say). You could also tweak the rules about when and what direction to round fractional levels. Clearly this requires a bit more bookkeeping than the written rules (and the multiclass caster rules are already confusing to many), but mostly only at level-up time.
What do folks think? Any broken dynamics I overlooked here? This is purely a thought experiment at this point; I have not played using this rule.
What do folks think? Any broken dynamics I overlooked here? This is purely a thought experiment at this point; I have not played using this rule.
By far the biggest issue here is that it's not user-friendly. The math is already too complicated, but having to check whether each spell you're considering is in one of your other class's spell list totally kills it.
Now we get down to personal preference. Multiclassing trades off access to higher level features for access to other class features that hopefully synergize well. Access to higher-level spells is the most significant feature you get as you reach higher levels as a spellcaster; in a way, these house rules are cheating the system by letting you skip ahead. Martial classes don't get to combine their levels working towards Extra Attack upgrades or ASIs.
Also, the only spellcasters that have enough in common to really synergize this way in my opinion are Arcane Tricksters, Eldritch Knights, and Wizards. I'm not feeling the idea that wizards and sorcerers have enough in common to cast Fireball at a higher level than their individual classes. Their methods of spellcasting are very different and the wizard's book learning doesn't translate over to the sorcerer's intuitive casting and vice-versa.
My only real gripe with the official multiclassing rules is that they punish partial casters. Their single-classed progression is based on dividing their level by 2 or 3 and rounding up, but the multiclassing rules require rounding down before adding them together. Rounding up before adding solves the issue. For example, a 5th level Eldritch Knight and a 4th level Arcane Trickster both have the same slots as a 2nd level wizard (5/3 and 4/3 both round up to 2). The official multiclass rules round both fractions down to 1 and assigns the combination a caster level of 2, when you'd expect them to add up to 4. The same 5th level EK also gains no slots when it gains its first wizard level; the official rules round 5/3 down to 1 and 1 + 1 = 2.
Yeah, the increased complexity is a clear downside, and having to track individual spells could be a headache for Divine casters who select from their full class list each long rest. In the typical case where you've got two classes, though, I think it'd just be a one time matter of highlighting the spells they have in common, either all at once or each time you level up and potentially have access to a new tier. This distinction is motivated by in-game realism more than game mechanics: if you are a 10th level character who is, say, Wizard 8 / Cleric 2, there's no reason to think that the time you spent developing your Clericness (Clericity?) would help you do Wizardy things better, unless those Wizardy things are also Clericky things. The pooled spell slot mechanic suggests that "doing magic" is a generic skill that transfers across classes; this rule just allows more specific intersections to transfer as well (though somewhat more inefficiently). If you don't want any transfer of this sort (which I gather you don't), I'm not going to argue. But I would suggest that multiclass casters usually sacrifice more than they gain in RAW (compared to other class combinations). Any particular combinations you think would be too overpowered with this rule?
As to the math, I think it's only slightly more complicated than finding your effective caster level, especially after your fix (which I'm a fan of!) of adding the fractions and rounding up at the end -- that actually requires adding fractions; this only requires multiplying them! You basically compute an "augmented caster level" for each caster class (which only updates at level up) by converting your levels to the equivalent in the other class if the classes have different caster fractions (mostly that means multiplying or dividing by 2 or 3), cutting the result in half, and rounding. You could just make a 3x3 table for all the pairings of full-, half-, and third-casters if you don't like doing mental arithmetic. Like so:
To calculate "borrowed" levels, find the caster fractions of the source and recipient classes and multiply your number of levels in the source class by the corresponding fraction in the table below, rounding down:
"To" Class Full | Half | Third =================== Full | 1/2| 1 | 3/2 | "From" Class Half | 1/4| 1/2 | 3/4 | Third| 1/6| 1/3 | 1/2 | ==================
I agree that AT or EK taking Wizard levels gets the clearest benefit from this, since they only have to worry about one spell list, so the augmented level automatically applies to all spells. But plenty of other combinations have lots of overlap too (Wizard and pretty much anything, Cleric/Paladin, Druid/Ranger, various combinations of Druid/Cleric/Bard might be others).
I think you could make the argument that something analogous ought to apply to the first Extra Attack, too. For example, a Fighter 4 / Barbarian X gets to count 1/2 of their Barbarian levels toward their extra attack feature, and hence gets Extra Attack at level 6. Or Fighter 3 / Barbarian X at level 7.
The pooled spell slot mechanic suggests that "doing magic" is a generic skill that transfers across classes.
It doesn't though. That's like saying swimming transfers to boxing. Your physical condition transfers over, but being a good swimmer doesn't help you be a good boxer. Spell slots represent endurance.
Regardless of how many spells a caster knows or prepares, he or she can cast only a limited number of spells before resting. Manipulating the fabric of magic and channeling its energy into even a simple spell is physically and mentally taxing, and higher- level spells are even more so.
It's also clear arcane and divine casters do things differently.
All magic depends on the Weave, though different kinds of magic access it in a variety of ways. The spells of wizards, warlocks, sorcerers, and bards are commonly called arcane magic. These spells rely on an understanding—learned or intuitive—of the workings of the Weave. The caster plucks directly at the strands of the Weave to create the desired effect. Eldritch knights and arcane tricksters also use arcane magic. The spells of clerics, druids, paladins, and rangers are called divine magic. These spellcasters’ access to the Weave is mediated by divine power—gods, the divine forces of nature, or the sacred weight of a paladin’s oath.
A cleric doesn't know how the spell functions; their deity helps make it happen. Their description even mentions they don't need to practice:
Harnessing divine magic doesn’t rely on study or training. A cleric might learn formulaic prayers and ancient rites, but the ability to cast cleric spells relies on devotion and an intuitive sense of a deity’s wishes.
Even within arcane casters, it's clear they're doing different things. Wizards rely on memorization and practice; sorcerers understand magic at an intuitive level; bard magic depends on putting their heart into it. Warlocks...are odd because they were supposed to be book-smart like wizards but the playtest feedback wanted them to be CHA casters, so they're the only class whose spellcasting ability goes unexplained.
But I would suggest that multiclass casters usually sacrifice more than they gain in RAW (compared to other class combinations).
Depends on where your priorities are and which classes are involved. Getting a whole second set of cantrips and low-level spells (possible rituals, too) is a pretty big benefit, and some classes like cleric and bard have strong first-level features.
Any particular combinations you think would be too overpowered with this rule?
A full spellcasting class taking a 2 level dip in another full spellcasting class can now gain features like Wild Shape, Channel Divinity or arcane traditions while only being 1 level behind in their common spells. E.g. Sorcerer X/Wizard (Bladesinger) 2, Bard X/Cleric 2, Cleric X/Druid (Moon) 2. These same combinations also get to prepare some level 2 spells on the 2nd level class.
That's another issue I have with these rules - they benefit you twice. Going back to magic basics shouldn't let you advance past where your highest-leveled spellcasting class would be single-classed. If the changes only gave your weaker classes a push, they'd be less problematic for me.
As to the math, I think it's only slightly more complicated than finding your effective caster level, especially after your fix (which I'm a fan of!) of adding the fractions and rounding up at the end -- that actually requires adding fractions; this only requires multiplying them!
That was a mistake on my part. I later realized you have to round up first and then add to get the correct results, and edited the post. Sorry!
I think you could make the argument that something analogous ought to apply to the first Extra Attack, too. For example, a Fighter 4 / Barbarian X gets to count 1/2 of their Barbarian levels toward their extra attack feature, and hence gets Extra Attack at level 6. Or Fighter 3 / Barbarian X at level 7.
You could, but then you run into issues where taking 2 or 4 levels in Barbarian is too good to pass up.
I later realized you have to round up first and then add to get the correct results, and edited the post.
Ah, I see. I guess I hadn't refreshed to see your edits. But I think you had it right the first time. If you round then add then you have the situation where a 9th level AT/EK hybrid, or a 3/3 Paladin/Ranger, has more slots than the corresponding single-class character. Same thing with a Paladin 3 / Ranger 3, say. If I'm not mistaken, RAW stipulates that you add together levels of the same "denomination" before rounding down, so an AT 5 / EK 4 is a 3rd level caster, just like a 9th level single class character of either class. But the issue isn't fixed by pooling only within denominations: consider a Paladin 6 / Eldritch Knight 6 deciding what to advance next. Under the round up then add rule, they get two full ECLs by going one of each for their next two levels but only one if they take them both in Paladin, supposedly more of a caster than the EK. In RAW, of course, you get nada at the next level and nada at the second level too unless both are Paladin levels (despite the fact that both single class Paladins and single class EKs get more slots at level 7). But if you add then round up, those two levels round up to one ECL regardless of the mixture (since it's a total of either 4/6, 5/6 or 1), which I think is clearly the best solution. The only downside I can see is that if you multi-class a half caster and a third caster, you might sometimes need to add thirds and halves together when you level up.
I guess my larger point is that minimizing math too much creates bizarre dynamics sometimes. I understand why WotC did what they did -- a lot of people are quickly turned off by having to do any calculations at all -- but unless your table is full of those people...isn't it better to use a system with better properties even if it's a little more complicated?
It's also clear arcane and divine casters do things differently. ... Even within arcane casters, it's clear they're doing different things.
I definitely take your point. In my mind that's the reason for the half-speed progress: half of being able to cast a spell is having access to the power source, and the other half is developing a feel for the actual casting (getting the verbal and somatic performance precise, for spells that have those, for example). It seems to me that improving your ability to channel magical energy as a sorcerer would let you more efficiently use your study time as a Wizard, and similarly having greater knowledge of the arcane would let you more effectively channel your sorcerer-y mojo. I think the swimming / boxing analogy is appropriate: training at swimming doesn't improve your boxing ability the same way that training in boxing would, but it likely makes your training in boxing more effective more quickly because you're a better athlete for it.
The front-loading of class features is an issue, though, I agree. Likely there would need to be some counterbalancing to make this work well.
I suppose you could define a system where you could explicitly designate a second class as an "adjunct class", where there'd be a tighter coupling (along the lines of this proposal for spellcasters, maybe extra attack and some form of ASI carryover) but an even further reduced set of features in that class. That'd have to be written case-by-case for each class though, I think, which would be a lot of work.
Alternatively you could make this rule narrower, targeted at the particular problem it was motivated by, which is that it's really hard to make an Arcane Trickster or Eldritch Knight more magical without paying a pretty high price, and say that you can only do this sort of thing within a spell list. Those use cases seem pretty balanced to me. Of course maybe the fundamental problem here is that there is no 50/50 rogue/caster class, nor is there a 50/50 fighter/caster class.
This sounds like it should function only for Eldritch Knights/Arcane Tricksters merging with Wizards. I'd say paladins and clerics as well as druids and rangers, but those two combinations actually have little in common with their spell lists at this point. Smites and bow spells really don't mix well with priestly and shamanistic spell lists.
The idea is based on finding spells that both classes can cast, and that's not a lot of spells outside of the wizardly based subclasses.
For reference I just did a quick glance through the Ranger and Paladin spell lists. Between 60 and 70% of Paladin spells are on the Cleric list and over 75% of Ranger spells are on the Druid list. I don't know whether that's an argument for or against this rule, but figured it'd be useful to have some numbers.
Edit: this is just based on PHB spells. May be that the lists diverge more in the other sources.
Ah, I see. I guess I hadn't refreshed to see your edits. But I think you had it right the first time. If you round then add then you have the situation where a 9th level AT/EK hybrid, or a 3/3 Paladin/Ranger, has more slots than the corresponding single-class character. Same thing with a Paladin 3 / Ranger 3, say.
They should have more slots than the corresponding single-class character though. A 3rd level single-classed Paladin or Ranger has the slots of a 2nd level spellcaster (⌈3/2⌉ = 2). Why shouldn't they also count as as 2nd level spellcasters for your multiclass spellcaster level? A paladin 3/ranger 3 should count as a 4th level spellcaster.
If I'm not mistaken, RAW stipulates that you add together levels of the same "denomination" before rounding down, so an AT 5 / EK 4 is a 3rd level caster, just like a 9th level single class character of either class.
But the issue isn't fixed by pooling only within denominations: consider a Paladin 6 / Eldritch Knight 6 deciding what to advance next. Under the round up then add rule, they get two full ECLs by going one of each for their next two levels but only one if they take them both in Paladin, supposedly more of a caster than the EK.
That's not any different from being 3/3 (or 7/7, 11/11, etc) and getting two ASIs back to back. You just happened to be at the cutoff point for your next upgrade in both classes.
But if you add then round up, those two levels round up to one ECL regardless of the mixture (since it's a total of either 4/6, 5/6 or 1), which I think is clearly the best solution.
Doing it this way results in lower spellcaster levels than the combination if their single classed equivalents though. Following the earlier example, you'd expect a Paladin 3/Ranger 3 to be a 4th level spellcaster, but the result will be 3rd level with the add-then-round-up approach.
I guess my larger point is that minimizing math too much creates bizarre dynamics sometimes. I understand why WotC did what they did -- a lot of people are quickly turned off by having to do any calculations at all -- but unless your table is full of those people...isn't it better to use a system with better properties even if it's a little more complicated?
For a home game, the best approach is always the one players prefer. When it comes to standard rules, playtesting has shown repeatedly that most people prefer simpler rules that they can keep in their heads and that don't slow down the game.
But like I mentioned earlier I don't think general multiclassing rules that produce results greater than the sum of their parts is a good thing; then there's no reason not to multiclass. I don't think the specific case of EK or AT with wizard would be problematic though, since they're identical spell lists and you'll never be more of a wizard than a full time wizard or more of a fighter/rogue than a full time fighter or rogue.
When it comes to standard rules, playtesting has shown repeatedly that most people prefer simpler rules that they can keep in their heads and that don't slow down the game.
Absolutely. But in this case the slightly more complicated arithmetic doesn't slow down the game because you only need to do it when you level up (or when you are planning your character), which presumably happens between sessions. Might take an extra minute or so to do; that's trivial compared to, say, selecting actual spells. It seems to me you can have any two out of the following three when it comes to spell slots: (1) don't penalize partial casters excessively, (2) ensure that "trading up" levels for more of a caster at worst keeps spell slots the same, (3) minimize arithmetic. "Round down then add" (RAW) achieves (2) and (3). "Add then round" achieves (1) and (2). "Round up then add" achieves (1) and (3).
That's not any different from being 3/3 (or 7/7, 11/11, etc) and getting two ASIs back to back. You just happened to be at the cutoff point for your next upgrade in both classes. ...
This isn't just about timing, though. A Paladin 13 / EK 7 is an 10th level caster under your rule, but a Paladin 14 / EK 6 is only 9th, despite their level balance being weighted more heavily toward a higher caster-fraction class. Even a Paladin 20 is only a 10th level caster which means swapping 7 full levels of 1/2 caster for 1/3 caster has no detrimental impact on your spell slots.
[Y]ou'd expect a Paladin 3/Ranger 3 to be a 4th level spellcaster, but the result will be 3rd level with the add-then-round-up approach. ... I don't think general multiclassing rules that produce results greater than the sum of their parts is a good thing
It seems to me a better comparison is not the sum of the parts but rather a single classed character in one of the two classes, since that's the alternative you actually have, not whether to be two single classed characters each of a lower level. When it comes to capabilities that both classes share, you shouldn't be able to go deeper with that capability by multiclassing than you could by not multiclassing. If when planning your first 6 levels you are choosing between Paladin 6, Ranger 6 or Paladin 3 / Ranger 3, why should the multiclass option make you a 4th level caster while the pure class options make you a 3rd level caster? Aren't the front-loaded benefits from two classes a big enough perk? The special case caveats in the multiclassing rules are all geared toward limiting or preventing stacking when two classes grant the same ability.
I don't think the specific case of EK or AT with wizard would be problematic though, since they're identical spell lists and you'll never be more of a wizard than a full time wizard or more of a fighter/rogue than a full time fighter or rogue.
We can agree on that, at least. Though minus the part about the identical spell lists (and the disparate casting techniques), the last clause applies to other combinations as well; you can't achieve same depth of a single classed character of your character level if you multiclass, though you can gain breadth. The borrowed levels rule would just reduce somewhat the depth penalty you incur. But I'm sympathetic to the idea that making this a general option makes certain combinations too powerful not to multiclass. At a minimum I'd probably couple this with a house rule restricting multiclassing to two classes.
This isn't just about timing, though. A Paladin 13 / EK 7 is an 10th level caster under your rule, but a Paladin 14 / EK 6 is only 9th, despite their level balance being weighted more heavily toward a higher caster-fraction class.
It might look weird, but it's still a matter of timing. Rounding before adding, whether up or down, means your spell slots only change on specific Paladin or Eldritch Knight levels; progress isn't shared between them. You just happened to pick 2 Paladin levels that map to the same spellcasting level, and 2 EK levels that map to different spellcasting levels.
If when planning your first 6 levels you are choosing between Paladin 6, Ranger 6 or Paladin 3 / Ranger 3, why should the multiclass option make you a 4th level caster while the pure class options make you a 3rd level caster?
You're right, I take it back. Add-then-round-up gives the results you'd expect. I hadn't noticed round-up-then-add sometimes ends up higher than the single-classed equivalent.
For comparison I did an AT / Wizard build, trying to exploit this rule to the greatest extent I could, trying to accelerate AT spell acquisition as much as possible without giving up too many rogue features. If you take AT 16 / Wizard 4, with Wizard levels at 5-6 and 15-16, you can get your 2nd level AT spells on schedule, get your 3rd level AT spells one level early, get three 4th level spell compared to two for a pure AT, two coming at levels 17 and 18 (instead of 19 and 20 as for a pure AT, and instead of getting no 4th level spells at all under standard rules), and a third at level 20, and if you allow bidirectional level borrowing, take up to four level 3 Wizard spells. Compared to single classing AT, you are 1 sneak attack die down for 10 levels and 2 dice down for 6 levels, lose spell thief for 4 levels, elusive for 3, and stroke of luck for 1, spend 8 levels down an ASI, delay uncanny dodge, evasion, and magical ambush and reliable talent by two levels each, and delay versatile trickster, blindsense, and slippery mind by four levels each. In exchange you get three caster levels of spell slots, three extra cantrips, ritual casting, arcane recovery, six extra level 1 spells, four extra up-to-level 3 spells, a level 2 wizard school feature, can upgrade one extra AT spell to level 4, and get level 3 spells one level early, and level 4 spells two levels early. I'd definitely take that deal, but it doesn't seem wildly unbalanced (at least not compared to other well chosen multiclass trades; and part of it is that the high level AT features aren't that great). In contrast, in standard rules, if you want a magic upgrade without losing access to level 4 spells, you either have to take at least 7 Wizard levels, at which point you've seriously cut into your roguishness, or limit yourself to 1; there's no in between.
What if it’s just: “when you level up, you can pick new spells based on your total spellcaster level if the spells in question are featured on the spell lists of _all_ your spellcaster classes.”? Then it stops you from going all over the place for versatility and getting higher levels of spells on top; if you want a multiclass with high level spells, you have to synchronise.
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It seems to me that the system for keeping multiple caster classes completely separate when it comes to the level of spells you can learn/prepare forecloses an obvious use case for multi-classing casters: namely when you have a "fractional caster" as your primary class and you'd like to dip into a full caster class as a way of trading away a bit of your martial side for a bit more of your magic side. As written, spending a level or two studying magic full time gives you a lot more breadth in your low level spell vocabulary, but it delays your ability to learn more advanced spells. This is true even if the full caster class uses the same spell list as your fractional class (i.e., if you are an Eldritch Knight or Arcane Trickster and dip into Wizard), which seems bizarre.
The pooled system for determining spell slots using an "effective caster level" (ECL) is really nice, and it seems like there ought to be a way to make use of that concept for spell lists as well, although it seems clear that the simplest rule along these lines: "you can learn/prepare any spell you have slots for", is overpowered and leads to ridiculous outcomes like a character with one Cleric level being able to prepare 9th level cleric spells. I propose the following compromise, which is a toned down version of a proposal from Orc Labs here, which I liked but thought was still a little too powerful.
To determine whether a character can learn/prepare a spell as part of their allotment in class X, start with the character's level in class X. Then for each other class, Y, that has that spell on their list, take the number of levels earned in class Y (no more than the number of levels in class X) and multiply that number by the ratio of caster fractions between Y and X (in other words, convert levels to a common currency), then divide by 2 and round down, and add the result (for example, if X is a 1/3 caster and Y is a full caster, multiply levels in Y by 1 / (1/3) / 2 = 3/2 and round down, adding the result to levels in X). The character can learn/prepare the spell if a single class character at the combined level could do so.
As a result, a half caster can dip into a full caster class for however many levels, and for the purposes of learning spells that both classes can cast, break even on their spell level progression pace (accelerating their spell slots and gaining some class features of the new class while giving up non-spell-related features of the original one). A 1/3 caster can actually accelerate their spell level progression, at least where shared spells are concerned, by taking at least two levels in a full caster class (two levels give the benefits of three levels in the original class, at the cost of some non-spell-related features).
How does this apply to other combinations, say a full caster taking levels in another full caster? For spells they have in common, a Wizard taking levels in Cleric, for example, will still advance the maximum level of Wizard spell they can cast, as long as a Cleric can cast it too, and at half the rate of taking additional Wizard levels. So a Wizard 10 / Cleric 10, for example, can learn spells on both lists like a level 15 Wizard or level 15 Cleric (i.e., up to level 8), but for spells on only one list, can only learn what a level 10 character could learn (i.e., up to level 5).
The choice of 2 as the number to divide "borrowed levels" by is arbitrary, and could be tweaked to make this more or less powerful (you could even use one number if the classes share a casting ability and a bigger number if not, reflecting greater or lesser similarity in the techniques used to cast the spell, say). You could also tweak the rules about when and what direction to round fractional levels. Clearly this requires a bit more bookkeeping than the written rules (and the multiclass caster rules are already confusing to many), but mostly only at level-up time.
What do folks think? Any broken dynamics I overlooked here? This is purely a thought experiment at this point; I have not played using this rule.
"Darvin" | Changeling | Hexblade 1 / Swords Bard 6 | Descent Into Avernus (AC 19; PP 14; 52/52 HP)
Anton Chergoba | Human | Battlemaster 4 | Lost Mines of Phandelver (AC 20; PP 14; 36/36 HP)
By far the biggest issue here is that it's not user-friendly. The math is already too complicated, but having to check whether each spell you're considering is in one of your other class's spell list totally kills it.
Now we get down to personal preference. Multiclassing trades off access to higher level features for access to other class features that hopefully synergize well. Access to higher-level spells is the most significant feature you get as you reach higher levels as a spellcaster; in a way, these house rules are cheating the system by letting you skip ahead. Martial classes don't get to combine their levels working towards Extra Attack upgrades or ASIs.
Also, the only spellcasters that have enough in common to really synergize this way in my opinion are Arcane Tricksters, Eldritch Knights, and Wizards. I'm not feeling the idea that wizards and sorcerers have enough in common to cast Fireball at a higher level than their individual classes. Their methods of spellcasting are very different and the wizard's book learning doesn't translate over to the sorcerer's intuitive casting and vice-versa.
My only real gripe with the official multiclassing rules is that they punish partial casters. Their single-classed progression is based on dividing their level by 2 or 3 and rounding up, but the multiclassing rules require rounding down before adding them together. Rounding up before adding solves the issue. For example, a 5th level Eldritch Knight and a 4th level Arcane Trickster both have the same slots as a 2nd level wizard (5/3 and 4/3 both round up to 2). The official multiclass rules round both fractions down to 1 and assigns the combination a caster level of 2, when you'd expect them to add up to 4. The same 5th level EK also gains no slots when it gains its first wizard level; the official rules round 5/3 down to 1 and 1 + 1 = 2.
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Yeah, the increased complexity is a clear downside, and having to track individual spells could be a headache for Divine casters who select from their full class list each long rest. In the typical case where you've got two classes, though, I think it'd just be a one time matter of highlighting the spells they have in common, either all at once or each time you level up and potentially have access to a new tier. This distinction is motivated by in-game realism more than game mechanics: if you are a 10th level character who is, say, Wizard 8 / Cleric 2, there's no reason to think that the time you spent developing your Clericness (Clericity?) would help you do Wizardy things better, unless those Wizardy things are also Clericky things. The pooled spell slot mechanic suggests that "doing magic" is a generic skill that transfers across classes; this rule just allows more specific intersections to transfer as well (though somewhat more inefficiently). If you don't want any transfer of this sort (which I gather you don't), I'm not going to argue. But I would suggest that multiclass casters usually sacrifice more than they gain in RAW (compared to other class combinations). Any particular combinations you think would be too overpowered with this rule?
As to the math, I think it's only slightly more complicated than finding your effective caster level, especially after your fix (which I'm a fan of!) of adding the fractions and rounding up at the end -- that actually requires adding fractions; this only requires multiplying them! You basically compute an "augmented caster level" for each caster class (which only updates at level up) by converting your levels to the equivalent in the other class if the classes have different caster fractions (mostly that means multiplying or dividing by 2 or 3), cutting the result in half, and rounding. You could just make a 3x3 table for all the pairings of full-, half-, and third-casters if you don't like doing mental arithmetic. Like so:
I agree that AT or EK taking Wizard levels gets the clearest benefit from this, since they only have to worry about one spell list, so the augmented level automatically applies to all spells. But plenty of other combinations have lots of overlap too (Wizard and pretty much anything, Cleric/Paladin, Druid/Ranger, various combinations of Druid/Cleric/Bard might be others).
I think you could make the argument that something analogous ought to apply to the first Extra Attack, too. For example, a Fighter 4 / Barbarian X gets to count 1/2 of their Barbarian levels toward their extra attack feature, and hence gets Extra Attack at level 6. Or Fighter 3 / Barbarian X at level 7.
"Darvin" | Changeling | Hexblade 1 / Swords Bard 6 | Descent Into Avernus (AC 19; PP 14; 52/52 HP)
Anton Chergoba | Human | Battlemaster 4 | Lost Mines of Phandelver (AC 20; PP 14; 36/36 HP)
It doesn't though. That's like saying swimming transfers to boxing. Your physical condition transfers over, but being a good swimmer doesn't help you be a good boxer. Spell slots represent endurance.
It's also clear arcane and divine casters do things differently.
A cleric doesn't know how the spell functions; their deity helps make it happen. Their description even mentions they don't need to practice:
Even within arcane casters, it's clear they're doing different things. Wizards rely on memorization and practice; sorcerers understand magic at an intuitive level; bard magic depends on putting their heart into it. Warlocks...are odd because they were supposed to be book-smart like wizards but the playtest feedback wanted them to be CHA casters, so they're the only class whose spellcasting ability goes unexplained.
Depends on where your priorities are and which classes are involved. Getting a whole second set of cantrips and low-level spells (possible rituals, too) is a pretty big benefit, and some classes like cleric and bard have strong first-level features.
A full spellcasting class taking a 2 level dip in another full spellcasting class can now gain features like Wild Shape, Channel Divinity or arcane traditions while only being 1 level behind in their common spells. E.g. Sorcerer X/Wizard (Bladesinger) 2, Bard X/Cleric 2, Cleric X/Druid (Moon) 2. These same combinations also get to prepare some level 2 spells on the 2nd level class.
That's another issue I have with these rules - they benefit you twice. Going back to magic basics shouldn't let you advance past where your highest-leveled spellcasting class would be single-classed. If the changes only gave your weaker classes a push, they'd be less problematic for me.
That was a mistake on my part. I later realized you have to round up first and then add to get the correct results, and edited the post. Sorry!
You could, but then you run into issues where taking 2 or 4 levels in Barbarian is too good to pass up.
The Forum Infestation (TM)
Ah, I see. I guess I hadn't refreshed to see your edits. But I think you had it right the first time. If you round then add then you have the situation where a 9th level AT/EK hybrid, or a 3/3 Paladin/Ranger, has more slots than the corresponding single-class character. Same thing with a Paladin 3 / Ranger 3, say. If I'm not mistaken, RAW stipulates that you add together levels of the same "denomination" before rounding down, so an AT 5 / EK 4 is a 3rd level caster, just like a 9th level single class character of either class. But the issue isn't fixed by pooling only within denominations: consider a Paladin 6 / Eldritch Knight 6 deciding what to advance next. Under the round up then add rule, they get two full ECLs by going one of each for their next two levels but only one if they take them both in Paladin, supposedly more of a caster than the EK. In RAW, of course, you get nada at the next level and nada at the second level too unless both are Paladin levels (despite the fact that both single class Paladins and single class EKs get more slots at level 7). But if you add then round up, those two levels round up to one ECL regardless of the mixture (since it's a total of either 4/6, 5/6 or 1), which I think is clearly the best solution. The only downside I can see is that if you multi-class a half caster and a third caster, you might sometimes need to add thirds and halves together when you level up.
I guess my larger point is that minimizing math too much creates bizarre dynamics sometimes. I understand why WotC did what they did -- a lot of people are quickly turned off by having to do any calculations at all -- but unless your table is full of those people...isn't it better to use a system with better properties even if it's a little more complicated?
I definitely take your point. In my mind that's the reason for the half-speed progress: half of being able to cast a spell is having access to the power source, and the other half is developing a feel for the actual casting (getting the verbal and somatic performance precise, for spells that have those, for example). It seems to me that improving your ability to channel magical energy as a sorcerer would let you more efficiently use your study time as a Wizard, and similarly having greater knowledge of the arcane would let you more effectively channel your sorcerer-y mojo. I think the swimming / boxing analogy is appropriate: training at swimming doesn't improve your boxing ability the same way that training in boxing would, but it likely makes your training in boxing more effective more quickly because you're a better athlete for it.
The front-loading of class features is an issue, though, I agree. Likely there would need to be some counterbalancing to make this work well.
I suppose you could define a system where you could explicitly designate a second class as an "adjunct class", where there'd be a tighter coupling (along the lines of this proposal for spellcasters, maybe extra attack and some form of ASI carryover) but an even further reduced set of features in that class. That'd have to be written case-by-case for each class though, I think, which would be a lot of work.
Alternatively you could make this rule narrower, targeted at the particular problem it was motivated by, which is that it's really hard to make an Arcane Trickster or Eldritch Knight more magical without paying a pretty high price, and say that you can only do this sort of thing within a spell list. Those use cases seem pretty balanced to me. Of course maybe the fundamental problem here is that there is no 50/50 rogue/caster class, nor is there a 50/50 fighter/caster class.
"Darvin" | Changeling | Hexblade 1 / Swords Bard 6 | Descent Into Avernus (AC 19; PP 14; 52/52 HP)
Anton Chergoba | Human | Battlemaster 4 | Lost Mines of Phandelver (AC 20; PP 14; 36/36 HP)
This sounds like it should function only for Eldritch Knights/Arcane Tricksters merging with Wizards. I'd say paladins and clerics as well as druids and rangers, but those two combinations actually have little in common with their spell lists at this point. Smites and bow spells really don't mix well with priestly and shamanistic spell lists.
The idea is based on finding spells that both classes can cast, and that's not a lot of spells outside of the wizardly based subclasses.
For reference I just did a quick glance through the Ranger and Paladin spell lists. Between 60 and 70% of Paladin spells are on the Cleric list and over 75% of Ranger spells are on the Druid list. I don't know whether that's an argument for or against this rule, but figured it'd be useful to have some numbers.
Edit: this is just based on PHB spells. May be that the lists diverge more in the other sources.
"Darvin" | Changeling | Hexblade 1 / Swords Bard 6 | Descent Into Avernus (AC 19; PP 14; 52/52 HP)
Anton Chergoba | Human | Battlemaster 4 | Lost Mines of Phandelver (AC 20; PP 14; 36/36 HP)
They should have more slots than the corresponding single-class character though. A 3rd level single-classed Paladin or Ranger has the slots of a 2nd level spellcaster (⌈3/2⌉ = 2). Why shouldn't they also count as as 2nd level spellcasters for your multiclass spellcaster level? A paladin 3/ranger 3 should count as a 4th level spellcaster.
The RAW isn't explicit about how to handle the addition and rounding, but according to Jeremy Crawford you divide, round down, then add.
That's not any different from being 3/3 (or 7/7, 11/11, etc) and getting two ASIs back to back. You just happened to be at the cutoff point for your next upgrade in both classes.
Doing it this way results in lower spellcaster levels than the combination if their single classed equivalents though. Following the earlier example, you'd expect a Paladin 3/Ranger 3 to be a 4th level spellcaster, but the result will be 3rd level with the add-then-round-up approach.
For a home game, the best approach is always the one players prefer. When it comes to standard rules, playtesting has shown repeatedly that most people prefer simpler rules that they can keep in their heads and that don't slow down the game.
But like I mentioned earlier I don't think general multiclassing rules that produce results greater than the sum of their parts is a good thing; then there's no reason not to multiclass. I don't think the specific case of EK or AT with wizard would be problematic though, since they're identical spell lists and you'll never be more of a wizard than a full time wizard or more of a fighter/rogue than a full time fighter or rogue.
The Forum Infestation (TM)
Absolutely. But in this case the slightly more complicated arithmetic doesn't slow down the game because you only need to do it when you level up (or when you are planning your character), which presumably happens between sessions. Might take an extra minute or so to do; that's trivial compared to, say, selecting actual spells. It seems to me you can have any two out of the following three when it comes to spell slots: (1) don't penalize partial casters excessively, (2) ensure that "trading up" levels for more of a caster at worst keeps spell slots the same, (3) minimize arithmetic. "Round down then add" (RAW) achieves (2) and (3). "Add then round" achieves (1) and (2). "Round up then add" achieves (1) and (3).
This isn't just about timing, though. A Paladin 13 / EK 7 is an 10th level caster under your rule, but a Paladin 14 / EK 6 is only 9th, despite their level balance being weighted more heavily toward a higher caster-fraction class. Even a Paladin 20 is only a 10th level caster which means swapping 7 full levels of 1/2 caster for 1/3 caster has no detrimental impact on your spell slots.
It seems to me a better comparison is not the sum of the parts but rather a single classed character in one of the two classes, since that's the alternative you actually have, not whether to be two single classed characters each of a lower level. When it comes to capabilities that both classes share, you shouldn't be able to go deeper with that capability by multiclassing than you could by not multiclassing. If when planning your first 6 levels you are choosing between Paladin 6, Ranger 6 or Paladin 3 / Ranger 3, why should the multiclass option make you a 4th level caster while the pure class options make you a 3rd level caster? Aren't the front-loaded benefits from two classes a big enough perk? The special case caveats in the multiclassing rules are all geared toward limiting or preventing stacking when two classes grant the same ability.
We can agree on that, at least. Though minus the part about the identical spell lists (and the disparate casting techniques), the last clause applies to other combinations as well; you can't achieve same depth of a single classed character of your character level if you multiclass, though you can gain breadth. The borrowed levels rule would just reduce somewhat the depth penalty you incur. But I'm sympathetic to the idea that making this a general option makes certain combinations too powerful not to multiclass. At a minimum I'd probably couple this with a house rule restricting multiclassing to two classes.
"Darvin" | Changeling | Hexblade 1 / Swords Bard 6 | Descent Into Avernus (AC 19; PP 14; 52/52 HP)
Anton Chergoba | Human | Battlemaster 4 | Lost Mines of Phandelver (AC 20; PP 14; 36/36 HP)
It might look weird, but it's still a matter of timing. Rounding before adding, whether up or down, means your spell slots only change on specific Paladin or Eldritch Knight levels; progress isn't shared between them. You just happened to pick 2 Paladin levels that map to the same spellcasting level, and 2 EK levels that map to different spellcasting levels.
You're right, I take it back. Add-then-round-up gives the results you'd expect. I hadn't noticed round-up-then-add sometimes ends up higher than the single-classed equivalent.
The Forum Infestation (TM)
For comparison I did an AT / Wizard build, trying to exploit this rule to the greatest extent I could, trying to accelerate AT spell acquisition as much as possible without giving up too many rogue features. If you take AT 16 / Wizard 4, with Wizard levels at 5-6 and 15-16, you can get your 2nd level AT spells on schedule, get your 3rd level AT spells one level early, get three 4th level spell compared to two for a pure AT, two coming at levels 17 and 18 (instead of 19 and 20 as for a pure AT, and instead of getting no 4th level spells at all under standard rules), and a third at level 20, and if you allow bidirectional level borrowing, take up to four level 3 Wizard spells. Compared to single classing AT, you are 1 sneak attack die down for 10 levels and 2 dice down for 6 levels, lose spell thief for 4 levels, elusive for 3, and stroke of luck for 1, spend 8 levels down an ASI, delay uncanny dodge, evasion, and magical ambush and reliable talent by two levels each, and delay versatile trickster, blindsense, and slippery mind by four levels each. In exchange you get three caster levels of spell slots, three extra cantrips, ritual casting, arcane recovery, six extra level 1 spells, four extra up-to-level 3 spells, a level 2 wizard school feature, can upgrade one extra AT spell to level 4, and get level 3 spells one level early, and level 4 spells two levels early. I'd definitely take that deal, but it doesn't seem wildly unbalanced (at least not compared to other well chosen multiclass trades; and part of it is that the high level AT features aren't that great). In contrast, in standard rules, if you want a magic upgrade without losing access to level 4 spells, you either have to take at least 7 Wizard levels, at which point you've seriously cut into your roguishness, or limit yourself to 1; there's no in between.
"Darvin" | Changeling | Hexblade 1 / Swords Bard 6 | Descent Into Avernus (AC 19; PP 14; 52/52 HP)
Anton Chergoba | Human | Battlemaster 4 | Lost Mines of Phandelver (AC 20; PP 14; 36/36 HP)
What if it’s just: “when you level up, you can pick new spells based on your total spellcaster level if the spells in question are featured on the spell lists of _all_ your spellcaster classes.”? Then it stops you from going all over the place for versatility and getting higher levels of spells on top; if you want a multiclass with high level spells, you have to synchronise.