There are so many discussions on Rule of Cool, Rules as Written, Rules as Intended. With nearly 3,000 seperate rules across 5e alone, it is nearly impossible to memorize every rule. Even DM's like Matthew Mercer and Brennan Lee Mulligan have admitted to often needing to look up rules and spells to see how they work. As such I have two questions.

What rules do you believe are unbreakable, never to be changed, absolutely canon rules to D&D?

Which rules have you changed for your campaign (i.e. I borrow secret death roles from XP to level 3, Resurrection rules from Matthew Mercer, and then have a few rules of my own such as the large party rule. {For each player above 4 add an exponential amount of health and power to the battles. If 5 and creature normally has 45 give the creature 70. If 6 then give the creature 120, if 7 then give the creature 180. This is balance and allow all players an opportunity to attack before the creature dies. As for attack, balance based on level and how much a player can take. A good rule of thumb is three hits to down a PC.}) 

Thank you for your opinions and please tell me how insane I am! :-)

Quote from clixism >>

What rules do you believe are unbreakable, never to be changed, absolutely canon rules to D&D?

My only unbreakable rules:
- DM decisions are final
- There's no wrong way to play as long as everyone's having fun
- There should be a 3rd but I can't think of anything else

The Rule of Cool and the Rule of Fun.

The rest is negotiation.

I note that I personally follow the Zero Rule and several of its caveats, as well as rule one. The GM is always right when the game is in session (start adding caveats), and All the Rules are Suggestions.

I listen to my players. All the rules, all the work, all the rest, depends on them having fun. If a class takes away their fun, the class goes.

the most core rules are around ability scores and how they are used (but not, I note, what they are or how important they are), combat, and action resolution (rolling for whatever).

I will note that if my players, as a group, ask me to rewrite everything from scratch, I do it. And check with them the entire time. My fun counts, too. That said…

I haven’t used an official setting since 1980, and I haven’t used an official module (sorry, adventure) since I9. I have created entirely new game mechanics and systems many times. I am still working on a magic point based system that I thought was done but I have tweaked a few times since then. I am currently redoing the combat action economy because of that. I have no sub-classes, 16 classes, and a crap ton of feats and more ability scores (9 plus 3 derived).

so of course I am going to say there are no sacred cows, lol. But I do think I am in a small minority, so take this with a big grain of salt.

Quote from AEDorsay >>

so of course I am going to say there are no sacred cows, lol. But I do think I am in a small minority, so take this with a big grain of salt.

 I'm pretty sure that's the vast majority opinion.  As long as your table is having fun, you're playing D&D correctly

I have personally been altering rules since my first read of a D&D book in like 85'.  The game is a mixture of game mechanics from every edition of the game since the 1st to the current.

That said, generally the point of any rule isn't for it to be religiously followed, but rather to always have a consistent baseline.  In short I mostly agree with the above, ensuring the game is fun, the outcome interesting and perhaps most importantly narratively logical and cool (the rule of cool)... 

That said, the rules of the game, at least the majority of them are related to combat and combat is as much a tactical/strategic affair as it is a narrative one, in most people's games the narrative element of combat is the story of the combat, rather than a free form narrative experience.  As such, rules are generally more rigidly followed during combat than they are anyway else and this I think is fairly normal/standard.  You want to know if you hit something, you make an attack roll, this is rarely "modified", its just a rule that is generally followed.

Its best I think as a DM to have a firm grasp of the combat rules in your game and execute them with a certain attention to consistancy.

In my games GM has final say, but I will hear from players before adjudicating if they objections.

Jeremy Crawford and Sage Advice are never considered. I've worked in publishing previously. If a company the size and profit of WotC cannot proof read and Quality Check prior to publishing, then contradictions and what they intended are irrelevent. They had their chance to have a say when publishing. 

Frankly though the rules are fuzzy anyway and often don't make a lot of sense because they were never really thought through. So it's a case of what is the right call for the right moment. Here's an example: Faerie Fire being cast on a Boneclaw. Faerie Fire creates a dim light outline around the creature such that it cannot turn invisible. However the boneclaw can hide in dim light. So let's say a player casts faerie fire on the boneclaw. Now the boneclaw cannot become invisible, but it can hide. 

Here's the complication - let's say the GM is running the boneclaw as having the ability to essentially melt away into the shadows and so doesn't need a physical object to hide behind because of their undead abilities. How then does Faerie Fire work? Well, in that situation my ruling is (and would be) that they are now outlined in the dim light and thus can be targeted without disadvantage normally applied for hiding. 

Let's change the scenario - the boneclaw is in a room with piles of rubble and coloumns and even a wardrobe. In that scenario I would rule that the boneclaw can hide and that faerie fire isn't going to negate the disadvantage.

There are many out there who will advocate for consistency without thought to just how badly thought through some of the interactions between spells and monsters can become when used in weird ways. What this ultimately means is that I tend to frame the rules and mechanics of 5e and the writers having created the flavour so the player doesn't have to. There are so many areas of grey where a GM has to interpret or adjudicate that I tend to say you have to take each situation as it happens. 

There are some areas where GMs can and should always be consistent - if you've decided that a multiattack be it from a a monster or a fighter's two attacks cannot target more than one enemy then that should always remain consistent. In fact I know GMs who do this in more hardcore campaigns. If however you're the GM that says that a multiattack can be split between targets then keep that consistent too. On top of this, I'm the type of GM who likes to present a challenge meaning that I don't bias in favour of the players. If I've accepted input on something like Faerie Fire for example then it works that way for both monsters and player characters. If I've ruled that you can only hide when there's something to hide behind - then that's the rule for both monsters and players. If the players really want to be able to hide without physical obstacles to hide behind then I make them aware that enemies can exploit that decision too - usually it's at that point they start to reconsider their protestations.

All of that said, it's your table. You are the one who gets to decide. What's the most fun for the group you've assembled. I've played at tables where all spell components are single use and are consumed by spell casting, where weapons can be broken, where injuries are possible and it makes for a very fun hardcore campaign as a player. That set up wouldn't work for any of my groups though. They just aren't into the tracking ammo, and weight, and components as groups. Every table dynamic differs, so ultimately it's about learning or setting a table style 'at this table we do x, y, and z'. That's what your session zero is partially for.

Rules I will follow:

1: If you are doing things by the book, then it works by the book. Making an attack? works as normal - the number of attacks, and how you roll for them, is unchanged, regardless of what you might want - "I want to elbow them i nthe face too", sorry, you're out of attacks. Meanwhile, someone who tries to drop off a cliff onto an enemy, they might be asked to roll a little differently!

Basically, I try to make the game predictable for the players - if they play by-the-book, moving and attacking and (frankly) being boring, then they will know exactly what to expect. Start jumping off things or climbing things, setting traps, and so forth, and that's when I just do what makes sense, and by-the-book be damned.

I play and dM fairly close to the rules, however having played from 1e on some older rules overlap or overwrite the 5e ones in my head soooo . Te one hard and fast one is that DM decisions in game stand. They can be discussed after the game but no extended arguing n game. Over the years I’ve found that RAW/RAI. Is a fairly balanced fun game, when you start going off that it’s easy to get unbalanced. I se play ne shots at moderate levels to test out homebrew creations for just that reason - think alpha and beta testing before full production runs

DM fiat but the DM is a host.
you roll what you roll, including the DM
all judgments should be fair and balanced.

I use most of the rules as written with some houserules and variants rules as well, sometimes possibly other limitations on races or subraces depending on the Campaign Setting. Here's some as exemples i've used in some of my games;

Ability Scores: A score of 18 is the highest one can reach, rather than 20, making the normal range of ability scores is 3-18 without magic.   

Alignment: Any except evil alignment allowed.

Roll Check: You describe what you want to do and the DM tells you what check to make, if any. No need to roll unnecessarily.

Slow Natural Healing: Characters don't regain hit points at the end of a long rest. Instead, a character can spend Hit Dice to heal at the end of a long rest, just as with a short rest. 

Long Rest Variant: At the end of a long rest, a character regains all spent Hit Dice. 

Healer’s Kit Dependency:  A character can't spend any Hit Dice after finishing a rest until someone expends one use of a healer's kit to bandage and treat the character's wounds.  

Opposed Check: Contest such as Dexterity (Stealth) or Charisma (Deception) check are made only when contest occur. For exemple, if a player character attempt to disguises or hides, no check is actually made until another creature can spot it somehow and contest check.

Falling: Falling damage is exponentially 10' = 1d6, 20' = 3d6, 30' = 6d6, 40' = 10d6, 50' = 15d6 etc: 

Death: Every time a character drops to 0 hit points, it gains a level of exhaustion. Deaths saving throws are rolled in private so the result is only known to the concerned player and DM. 

Leveling Up: Leveling up is achieved through milestone at DM’s discretion. 

I think one of the most oft-overlooked rules, but most important behind the scenes, is the rule of "Specific Beats General." I feel like many rules disputes I've seen eventually boil down to one person in the debate not reading the correct order of operations, citing some general rule and overlooking/ignoring a specific rule that countermands it.

Classes, in a sense, are collections of specific instances where general rules are superceded or skirted around in different ways, when you look at it that way. For instance if I had a DM tell me that my swashbuckler rogue NEEDED advantage in order to sneak attack, they might be right about the general rule that advantage grants sneak attack, but they would be wrong in ignoring rakish audacity, an ability that grants me a way around that rule for an additional means of getting sneak attack. All class abilities, spells, and feats essentially operate off the principle of providing a specific rule that gets around a general restriction otherwise imposed.

So, following the template set forth above, some of my specific rules:

• 9 Ability scores plus 3 derived. I renamed Intelligence into Knowledge, split the perception checks off into their own ability score, brought in Sanity, and added a score called Mana because we use a magic point system that has significant impact on pretty much all magic in the game. Then we have Heart, Vitality, and Psyche. Real World Playing Change? Balanced out the importance of different scores. Starting Cap at Creation is 20, actual Cap is 30.
• Minimum Ability Scores: None. There is no minimum score for any race or class. Everyone does get an additional 2 points for wherever (and now they have 12 "whereevers", because you can use them on the derived scores, as well).
• Races: all are Heritages. Each of them has a Tradition (which includes some core Values and family structure), Talent, Trait, and Limit.
• Backgrounds: There are generally always Two types: Circumstance and Opportunity. Occasionally a story for a campaign may require a third. Circumstances are basically the "thing risen above", and Opportunities are "how you learned to live". Backgrounds do not give ability score increases.
• Homelands: where they came from. These includes folkways, values, attitudes, and odds and ends.  Backgrounds are generic enough that they can be used with any homeland and one of the core rules for them.
• Metamagic: there is no sorcerer class, and metamagic is technically available to everyone, because you can spend additional mana to alter a spell at time of casting. 
• Exhaustion: That Vitality score? Yeah, this is where it comes into play. different system, because using magic is tiring. 
• Damage types: I got lots of them.
• Unified Spell Damage: spells cause damage based on the level of the caster and the level of the spell. Caster determines number, spell level determines the die type used. This makes a cantrip in the hands of a 20th level Wizard who is really angry something you do not want to meet, lol.
• More Elemental Spells: There is basically a form of attack and a form of defense for each of the multiple elements at each Spell Level.
• Degrees of Mastery: each of the "tiers of play" basically matches back to a "degree of Mastery", and that is joined by a title that is used in role playing and describes the competency of a particular person (novice, adept, maser, etc).
• Classes: Called Professions, there are no subclasses, and there are 16 distinct classes who all have abilities that no one else can use. They do not match any published class, and do not follow the same structures as DDB classes. 
• Aspects: take all the feats, special abilities, and other things you can get, put them all into a big ole chart, and then allow them to be taken by anyone when they reach certain levels. The specific class abilities are not included, but there are Disciplines, Veiled Knowledge, Esoterica (feats, basically), Combat Orders, Magical Mysteries. Although they are counted normally under proficiencies, among the Disciplines are also using armor and using weapon types. Half casters get to choose between a Combat Order or a Magical Mystery -- and access to spells is governed by this as well.
• Weapons: some changes here, predicated on the idea that the user grants capabilities to a weapon instead of the weapon granting capabilities to the user. 
• Rituals: all spells have a ritual form. One does not always want to cast them, though, lol. Apparently, fireballs tend to incinerate the folks in the ritual. All rituals require material components, and can be done by anyone who follows the ritual and has the power (individually or collectively).
• Spells: All spells have Verbal and Somatic Components. All spell casting causes a manifestation to appear around the caster -- so no sneaky casting. The higher the level of the spell, the longer it takes to cast -- this impacted the way action economy works, as well. 
• Difficulty: 30 different levels.
• Size: the entire size system was redone.
• CR: CRs were re-done. They run from 1 to 50.
• Magic Types: Arcane, Divine, Eldritch, Mystical, and Primal. Each has a distinct list, but everyone can pull from the Elemental list (which is part of all of them). Classes are linked to a particular kind of magic (bards use mystical, witches use primal, wizards use arcane, etc). There is also a way to do mage duels.
• Psionics are included -- they require effort to learn, and getting them means sacrificing a choice gained as you level up -- so for example, instead of taking a magical mystery, you take telepathy instead.  It allows for someone to be any class, but rather than have some of the traditional capabilities of that class, they have a lot of psionic abilities instead.
• There are nulls -- they have an automatic resistance to magic. This does include both malicious and beneficial magic -- they are harder to heal.

Those are some of the things I have done with rules in my game. One of the biggest things I focus on is consistency, as well -- a ruling  once is the same for that cirustance in all equal circumstances. 

Lastly, I reward "damn fool heroics" -- this one is very much dependent on the moment, but really comes down to those things one does that involve potential sacrifice, daring-do, and good play value. One of the kids said it is like Han Solo in Star Wars charging the storm troopers around the corner, then charging back away from them. They were not wrong. I tend to use the example of standing at the edge of a deep dark pit and not knowing what is down there or how deep it is, but jumping anyway because you'll find out eventually.

I do expect common sense -- a feather fall for the jump is wisdom.

i will note that a lot of my rules are adaptations of long running things we settled years ago, ideas and requests of the player group (we've never done magic point systems until now, and playtesting has been a blast), and when I get stumped I almost always turn to 1e first.  I have a lot of environmental rules that are essentially cribbed from spell effects (a blizzard is a lot like a cone of cold), but I also have a strong "exploration" bent to my last four or five worlds.

Average campaign length is 3 years for me. Most campaigns take me a year to plan, and happen while I am running the current one. If I change a world, there is a bum, as the rules have to fit the world, not the other way around, which is perhaps my biggest personal rule:

The game's rules need to fit to the setting's rules. A setting where there are no giants doesn't need rules for giants, and rules for a class or a race that doesn't fit the world don't either..

What rules do you believe are unbreakable, never to be changed, absolutely canon rules to D&D?
For the most part, I  play combat very close to the way it's written. Occasionally, I'll fudge something if the players want to do something clever. I'll also make a ruling based on what I think was intended in the rules and not what's written (Example: You can't fall 150 ft, drop a character at the last second and then fly away so you don't take the falling damage yourself. I can see how you could interpret the rules that way, but that was definitely not what was intended and I'm not opening that door. It's just easier to keep things the way they're written so that I'm not constantly having to make a bunch of DM calls in the moment.

Which rules have you changed for your campaign?
I find that inspiration doesn't get a lot of use as it's written. Instead, I give players the option to reroll a failed dice roll rather than gaining advantage on the roll.

I would say that there are no entirely unbreakable rules, it's really a question of magnitude of changes; too many changes and it stops feeling like D&D.

Quote from Pantagruel666 >>

I would say that there are no entirely unbreakable rules, it's really a question of magnitude of changes; too many changes and it stops feeling like D&D.

 
this is truth, and as an unusual example of this...

I skipped 3.5 and 4. I played 2e for a very long time before moving to 5e. My immediate (and still ongoing) emotional reaction is that it doesn't feel like D&D to me.

... and yet, when it comes down to it, it still plays like D&D. Yes, the rules are different and how you do things is different and some of the stuff is coming from a very different perspective, but it is still D&D.

The thing we have discovered that really shifts that is when you screw with getting rid of d20 or try to drop classes for a skill based system or you mess with the baseline mechanics of how rolls operate, or you change all the spells, then you lose that feel.

But we've played D&D in the modern world (with classes like Stockbroker, lol) and it still felt like D&D. Our experience is less related to setting and more about the way the game works.

Which I say even as I note that we collectively tried Pathfinder several times. ANd not a one of us liked it, because, and I quote many an argument: it doesn't feel like D&D. (insert eyeroll here)

A lot of it does rely on how the players feel about things, though. A lot of folks would read my list of things and say "that doesn't sound like D&D", and some of my players would look at some of the house rules they've encountered and say "that doesn't sound like D&D".  It is deeply subjective at the collaborative level.

You can *add* to D&D. Taking away from it is where the problems tend to start.

Quote from clixism >>

What rules do you believe are unbreakable, never to be changed, absolutely canon rules to D&D?

 

Monsters and PCs play by the same rules.

Monsters are generated differerently to PCs, but in play follow the same rules. Action, Bonus Action, Movement, Reaction, spell components, things like that. If PCs can move between attacks then so can monsters. If PCs can't cast while manacled then neither can monsters. There will of course be exceptions for special monsters, but those are rare.

Or to put it another way, core mechanics are symmetric. For example, attack rolls miss if the number is <= AC. It doesn't matter of the attacker is a PC or NPC.

I say this because my current game (Modiphius 2d20) is not like this. Many rules are asymmetric., For example, in any tie the players win, regardless of who initiated the test.

Quote from AEDorsay >>

Which I say even as I note that we collectively tried Pathfinder several times. And not a one of us liked it, because, and I quote many an argument: it doesn't feel like D&D. (insert eyeroll here)

 

Mechanically, Pathfinder 1E is very similar to 3.5. The way they designed their adventures, though, is very different. They tend to have a much darker tone and I often felt like the designers went out of their way to frustrate any action the players might want to take. I tried to turn to Pathfinder after 4E, but since it wasn't that different from 3.5 and I didn't like the adventures, I just stuck with 3.5.

Now, I prefer 5e over 3.5. It's much more streamlined. That said, the feats and prestige classes of 3.5 allowed for a lot more variation and complexity. It was also playtested a lot more at higher levels. If you like the mechanics of Pathfinder, give 3.5 a shot.

Quote from DoveArrow >>

Quote from AEDorsay >>

Which I say even as I note that we collectively tried Pathfinder several times. And not a one of us liked it, because, and I quote many an argument: it doesn't feel like D&D. (insert eyeroll here)

 

 

Mechanically, Pathfinder 1E is very similar to 3.5. The way they designed their adventures, though, is very different. They tend to have a much darker tone and I often felt like the designers went out of their way to frustrate any action the players might want to take. I tried to turn to Pathfinder after 4E, but since it wasn't that different from 3.5 and I didn't like the adventures, I just stuck with 3.5.

Now, I prefer 5e over 3.5. It's much more streamlined. That said, the feats and prestige classes of 3.5 allowed for a lot more variation and complexity. It was also playtested a lot more at higher levels. If you like the mechanics of Pathfinder, give 3.5 a shot.

I didn't like 3.5 or Pathfinder, myself. A couple of my longest term players enjoyed 3.5 but most of us ended up going with whatever the DM at the time was running (so for me that was the old 2e stuff). Only of our our collective DMs is really interested in running any formal adventures, the rest of us make our own and all of us have very different ways of doing that, lol. None of us went to 4e. The timing was bad, more than the game set up was in our case. 5th was picked up with much happiness.

I have relatively few complaints about 5e, and the stuff we collectively are doing for Wyrlde is more or less solving all of them. perhaps the three biggest complaints are that it is over simplified, that classes are a pandering problem, and that they didn't develop out the options. ALl of which are my problem, and I'm solving them.

So we are using 5e as our base (spells, unchanged monsters, special abilities, underlying mechanics) and adjusting it to suit.  A lot of the "meta" level stuff in the playtesting has been making us laugh because we were doing a lot of the same stuff already so in some cases we just dropped that stuff in directly.

Quote from clixism >>

There are so many discussions on Rule of Cool, Rules as Written, Rules as Intended. With nearly 3,000 seperate rules across 5e alone, it is nearly impossible to memorize every rule. Even DM's like Matthew Mercer and Brennan Lee Mulligan have admitted to often needing to look up rules and spells to see how they work. As such I have two questions.

 

I think this is the case for every Dungeon Master ever, honestly. As you said yourself, memorizing half a dozen plus books of rules and extra content is near impossible. 

Quote from clixism >>

What rules do you believe are unbreakable, never to be changed, absolutely canon rules to D&D?

None. It depends on the table, but I don't think there's any rule overall in D&D that is untouchable or can't be changed if everyone really wants it to.

Personally, I almost never change rules in the moment,  but I do have a few house rules or very minor modifications that I've made beforehand - such as the Matt Mercer potion one - because I feel the way the core rulebooks treat these mechanics suck. For me, the rules aren't sacred cows and I don't see many, if any, who act like they're such. However, I like to be consistent with enforcing my mechanics and attempt to never abruptly change rules without talking to the group first.

I try and play the rules as written - I can't see the point of paying a large amount of cash for a set of rules and then not actually use them. If you don't like the rules then get a game that better suits what you want.