Monstrous Compendium Vol. 1: Spelljammer Creatures
Frozen Sick
D&D Beyond Basic Rules
Basic Rules (2014)
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Monstrous Compendium Vol. 1: Spelljammer CreaturesFrozen SickD&D Beyond Basic RulesBasic Rules (2014)Sign in to view your library & saved favorites.
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Something I've been thinking about writing for a while...
Understanding Action Economy Correctly
It's conventional to declare that groups in D&D are disproportionately dangerous due to 'action economy', but a bit of inspection shows that this is oversimplified: a half dozen bandits have a big action economy over a purple worm, but no-one would think the bandits are more dangerous. On the other hand, they might well be more dangerous than a bandit captain. The proper way to look at this is:
The threat an enemy poses is equal to the number of actions they get over the course of an encounter, multiplied by the value of those actions.
How Numbers Influence Threat
Let's say our party of PCs can drop one monster per round on average. Against one monster, that means (depending on initiative order and luck) the monster goes zero or one times; against multiple, while the first monster goes zero or one times, the second monster goes one or two times, the third goes two or three times, and so on. The expected number of monster actions, and thus the total threat, winds up being (number of monsters) * (number of monsters) * 1/2. This may be familiar as Lanchester's Square Law.
The above assumes that all the monsters can take effective actions. If this is not the case the advantage of numbers is reduced; for example, if you're fighting in a choke point where only one monster can attack at a time, the threat of a group of monsters is linear in the number of monsters (Lanchester's linear law). The threat of a groups can also be reduced by the use of area effects. You can make those laws more general by introducing a Lanchester exponent, indicating the true power of numbers, which is 1 for the linear law, 2 for the square law, but can have other values for specialized situations; 1.5 (N*sqrt(N)) is a fairly common approximation for modern warfare.
Understanding 2014 Monster and Encounter Building
The 2014 rules appear to have been designed by someone familiar with the scaling I discuss above, because it turns out the xp value of a monster can be approximated as (dpr) * (hp) * 2 / 3. If we assume that HP are a proxy for mean survival time, which seems like a fair assumption, the xp value of a monster is just equal to its expected damage against a standardized party. The 'group size' modifier is roughly equal to the square root of the group size, so it turns out that adjusted encounter XP is equivalent to a lanchester exponent of 1.5.
While this model is mathematically justified, it has two problems: it works very poorly when monsters have different xp values, and it's a big pain to actually use.
2024 Monster and Encounter Building
The 2024 rules do not appear to have been written by someone who understands Lanchester's Laws, because there are really only three significant differences from 2014: monsters do about 20% more damage at the same xp value, actual budget values got tweaked, and the group size modifier got killed. The last is a serious problem, because it means groups of monsters are dramatically more dangerous than single creatures at the same xp value, unless you happen to be fighting in a situation where the Lanchester exponent is 1.
How the power of numbers varies with encounter design
While 2014 used a Lanchester exponent of 1.5, and 2024 uses 1.0, the actual appropriate value can very quite a bit with encounter design. The big factors to consider are
If none of those apply, the exponent winds up at 2; a large number of ranged enemies in an open field battle is a big problem. Also, note that this same list of factors determines how effective the PCs are against the monsters.
When Action Economy Really Matters: Status Effects and Non-Damage Actions
In a simple slugging match, it doesn't actually matter whether an enemy gets 1 action for 20 damage or 4 actions for 5 damage -- either one winds up being 20 damage. However, this dramatically changes when dealing with status effects, because the value of a status effect is equal to the change in value of the actions it affects. Stun a monster that does 5 damage per round and you've prevented 5 damage; stun a monster that does 20 damage per round and you've prevented 20 damage. This also applies to buffs -- cast bless on someone who attacks once per round for 8 damage and it's worth an average of 1 damage per round, cast it on someone who attacks twice for 16 and it's worth 4 damage per round. This is why monsters intended as solo bosses need methods (legendary resistance, immunities) of dealing with status effects, and conversely, weak monsters with incapacitating status effects can be a threat entirely out of proportion to their nominal power.
This is also an issue for non-damaging effects. For example, let's say you're up against a guard captain. Under normal conditions, if he has a pair of guard with him, they're barely relevant... but if there's an alarm bell that takes an action to ring, it's suddenly very important that there's a guard available to run off and ring the bell while the captain fights.
This...is really important. Can homebrew balance this out? I've always been sort of unhappy with DnD combat. I feel like players either don't get enough actions, or actions don't matter as much as they should. I feel that players should be more dangerous; it feels ridiculous that it could take two, maybe even three player actions to down a relatively inconsequential enemy because they don't want to use their serious abilities on low CR creatures. And yes, low CR creatures with crippling status effects are awful.
Super useful, thank you! In this part especially you put your finger on the biggest issue I have with current monsters/combat: "monsters do about 20% more damage at the same xp value... and the group size modifier got killed."
I've found that in the 2024 rules, everyone is a glass cannon. It's made the game incredibly swingy. By now, I generally either halve the dice or drop the modifiers from every monster's damage because otherwise a single bad roll can absolutely paste the players.
That may be an issue of play style or tier; I'm generally fine with monster damage levels in 2024 (just don't use PC builds for NPCs or monsters).
Interesting, I was about to commit this sin. Why would you say not to use PC stats for NPCs?
If you use PC stats for NPCs, they will be glass cannons (mostly). If you don't want your NPCs to be glass cannons, that's bad.
The other big reason to not use PC stats for NPCs is that it's a lot of work.
Maybe play style differences? I completely agree with you on not using PC builds for monsters and NPCs. It always seems very cool, and it just doesn't work. But otherwise, I've been finding that if I stick to the encounter XP builds as recommended by the book, my players either wipe the floor with the monsters easily or someone gets basically one-shotted. Rarely anything in between.
Well, this is 5/5.5e. Someone getting oneshotted is no big deal, it just gives the healer something to do. My general standard is that any fight where the monsters can't drop one PC a round is too easy. If you don't like that style, you pretty much need to build custom monsters with very high hit points relative to their offensive power.
If people are curious, I did some math in this post. The first set of tables is exactly the same as existing rules for High difficulty. The second set applies an effect equivalent to a lanchester exponent of 1.5. Thus, for a party of 4 at level 10
Can I ask what consideration you made for the following three factors:
- Magic Items (how do they skew the exponent, if they do?)
- Multiclassing (does this affect the calculations at all?)
- For 5e only, Feats (as they're optional, do they affect the calculations?)
DM session planning template - My version of maps for 'Lost Mine of Phandelver' - Send your party to The Circus - Other DM Resources - Maps, Tokens, Quests - 'Better' Player Character Injury Tables?
Actor, Writer, Director & Teacher by day - GM/DM in my off hours.
Absolutely none. I merely assumed that the budget per PC in the 2024 rules is correct when dealing with one monster per PC (is that true? Probably not) and adjusted everything else for a lanchester exponent of 1.5 instead of 1. The claim is not "this will give you a balanced encounter", it's "an encounter with a solo monster and an encounter with multiple monsters are likely to be similar in real danger", which is decidedly not the case in 2024 as written.