NPC Hit Dice

[EggKookoo]

Has there ever been a formula or calculation provided for how monsters and other NPC hit dice amounts are determined? I know the die type correlates to the creature's size. I mean the actual number of dice.

For example, the bandit has 2d8 + 2 HP. This makes sense, he has a Con mod of +1, so two hit dice. But why two hit dice? Was it just that the devs wanted to give him a CR of 1/8, and set his HP average to be something that fit with that CR, and then being a medium creature, it needed two d8s to get there?

Another example is the cult fanatic, with 6 hit dice. He's described as a "4th level caster" which could sort of justify him getting four extra hit dice (over the two that maybe he might get for the same reasoning as the bandit).

But then there's the berserker, with nine hit dice.

Is it no more structured than the devs wanted a creature to have a CR of X, and set the HP to match, and then worked out the hit die formula based on that?

[Segev]

Has there ever been a formula or calculation provided for how monsters and other NPC hit dice amounts are determined? I know the die type correlates to the creature's size. I mean the actual number of dice.

For example, the bandit has 2d8 + 2 HP. This makes sense, he has a Con mod of +1, so two hit dice. But why two hit dice? Was it just that the devs wanted to give him a CR of 1/8, and set his HP average to be something that fit with that CR, and then being a medium creature, it needed two d8s to get there?

Another example is the cult fanatic, with 6 hit dice. He's described as a "4th level caster" which could sort of justify him getting four extra hit dice (over the two that maybe he might get for the same reasoning as the bandit).

But then there's the berserker, with nine hit dice.

Is it no more structured than the devs wanted a creature to have a CR of X, and set the HP to match, and then worked out the hit die formula based on that?

The DMG has a section on building monsters. Yes, the number of HD is pretty well set by CR.

[EggKookoo]

The DMG has a section on building monsters. Yes, the number of HD is pretty well set by CR.

Right, I was just trying to determine if there was a design philosophy beyond "I want CR X, set HP to Y (among other params like AC), work out reasonable HD formula to get to Y."

The cult fanatic being a 4th level caster has nothing to do with it getting four "extra" HD.

[Segev]

Right, I was just trying to determine if there was a design philosophy beyond "I want CR X, set HP to Y (among other params like AC), work out reasonable HD formula to get to Y."

The cult fanatic being a 4th level caster has nothing to do with it getting four "extra" HD.

No, as far as I can tell from reading the DMG, it is literally what you said: "I want CR X, set HP to Y (among other params like AC), work out reasonable HD formula to get to Y."

[Ninja_Prawn]

As someone who writes monsters semi-professionally... yep. You decide what CR you want then guesstimate a number of hit dice based on that. There's no science to it. After a while you do get a feeling for how many HD you want a monster to have, and if the CR doesn't stack up, you tinker with damage resistances, save proficiencies, etc. until it works.

[EggKookoo]

As someone who writes monsters semi-professionally... yep. You decide what CR you want then guesstimate a number of hit dice based on that. There's no science to it. After a while you do get a feeling for how many HD you want a monster to have, and if the CR doesn't stack up, you tinker with damage resistances, save proficiencies, etc. until it works.

Awesome, thanks. I just wanted to make sure I wasn't missing a chef's secret somewhere.

Since you're on the line, as someone who has a lot of monster-gen experience, do you find CRs hold up in general? Meaning it's reasonable to expect a consistent amount of threat or challenge for a given CR, regardless of the actual mix of HP, AC, Prof Bonus, and so forth? I understand there will always be outliers and dice will rule the actual encounter in the end. I just mean is there a good bell curve to the outcome?

[Asisreo1]

It's kinda weird, though right? If you're making a creature that's medium but then you choose to keep all the stats the same except for the size, they'll end up with more HD if they're smaller and less if they're bigger. This means that a tiny creature's injuries are healed more consistently than a large creature with all other stats the same.

[Segev]

It's kinda weird, though right? If you're making a creature that's medium but then you choose to keep all the stats the same except for the size, they'll end up with more HD if they're smaller and less if they're bigger. This means that a tiny creature's injuries are healed more consistently than a large creature with all other stats the same.

Yes, but consider the use-case: generally speaking, you don't give monsters short rests to heal.

I'm not saying it doesn't happen - it does - but it's a bit unusual.

[Ninja_Prawn]

Since you're on the line, as someone who has a lot of monster-gen experience, do you find CRs hold up in general? Meaning it's reasonable to expect a consistent amount of threat or challenge for a given CR, regardless of the actual mix of HP, AC, Prof Bonus, and so forth? I understand there will always be outliers and dice will rule the actual encounter in the end. I just mean is there a good bell curve to the outcome?

Ehhhh my feeling is that CR is a deeply flawed system. I use it by-the-book because I'd be constantly catching flak from stats nerds if I didn't, but I don't really believe it's a good rating of challenge. There's just too many variables, things that the system doesn't take into account, the vagaries of PCs and party compositions... and I mean, the whole thing is based on the idea that combat lasts 3 rounds. But like, even if that is true on average, there will always be longer and shorter combats, which could cause some features/abilities to be significantly more or less powerful than they would be in a 3-round fight.

As a DM, you have to view CR as the roughest of guides. Your judgement and knowledge of your players is much more important when building encounters.

[Segev]

Ehhhh my feeling is that CR is a deeply flawed system. I use it by-the-book because I'd be constantly catching flak from stats nerds if I didn't, but I don't really believe it's a good rating of challenge. There's just too many variables, things that the system doesn't take into account, the vagaries of PCs and party compositions... and I mean, the whole thing is based on the idea that combat lasts 3 rounds. But like, even if that is true on average, there will always be longer and shorter combats, which could cause some features/abilities to be significantly more or less powerful than they would be in a 3-round fight.

As a DM, you have to view CR as the roughest of guides. Your judgement and knowledge of your players is much more important when building encounters.

3 rounds? Really? ...huh, they did a pretty good job calibrating that in my experience, then. That's usually about how long a combat takes.

[Ninja_Prawn]

Yeah, it's not a bad assumption, for sure. But it's still pretty crude.

Like, if a monster has a Recharge 5-6 ability, you assume it uses it once in 3 rounds... but if it's Recharge 6... it still uses it once in 3 rounds. So you treat them the same for the purpose of CR, but if a combat goes to 6 rounds, the one with the higher recharge chance could be pumping out way more damage. Likewise, damage-over-time and regeneration are treated as being active for 3 rounds, so for monsters that are reliant on regeneration for their defense, they'll underperform if you can hit them hard and fast in round 1.

[Sam113097]

3 rounds? Really? ...huh, they did a pretty good job calibrating that in my experience, then. That's usually about how long a combat takes.

That's actually one of the things that I enjoy about 5e: combats are quick and decisive. It makes it easier to keep narrative momentum when the fights last minutes as opposed to hours.

Speaking of CR, I'm no expert, but in my experience as a DM, it's sort of a crapshoot. 2 combats of the exact same CR can vary significantly in difficulty based on what your party does and what their weaknesses are. As Ninja-Prawn said, you have to adjust based on what you know about your PCs.

[Segev]

Actually, in my experience, fights in PF1 and 3.5 tended to take 1 to 1.5 rounds, tops. ^^; And still last hours IRL. Though that's over IRC, which does slow down actually running combat.

[EggKookoo]

As a DM, you have to view CR as the roughest of guides. Your judgement and knowledge of your players is much more important when building encounters.

This mostly jives with my experience. I find it hard to know, since a couple of bad rolls in a row on one side or the other can really tip the battle, CR be damned. It's also hard to know because the PCs will typically win at a fairly tough encounter -- they'll just have to pull out the bigger guns to do so. And the consequence of that usually comes into play the next encounter, or the last encounter before they call it a day and go for a rest. It's not easy to see that the party rested when they did not because of that last fight, but because they burned through their spell slots three fights ago. I mean, unless you're tracking these things...

[Lunali]

Awesome, thanks. I just wanted to make sure I wasn't missing a chef's secret somewhere.

Since you're on the line, as someone who has a lot of monster-gen experience, do you find CRs hold up in general? Meaning it's reasonable to expect a consistent amount of threat or challenge for a given CR, regardless of the actual mix of HP, AC, Prof Bonus, and so forth? I understand there will always be outliers and dice will rule the actual encounter in the end. I just mean is there a good bell curve to the outcome?

CR isn't a good measure of threat. It's a measure of how long it will take to kill a creature and how much damage that creature will do in that time. It works decently for creatures that just take damage and do damage, not as well for anything else.