D&D 5E Adding class levels to a monster - how much does the CR increase?

Caliban

Rules Monkey
I'm gearing up to run a new campaign, and I plan on adding class levels to various humanoid creatures. Thing is, I'm not sure how much that affects their CR. Some of the NPC casters in Volo's guide and the MM have caster levels well above their challenge rating.

Is it a 1-to-1 ratio if they have full class abilities and a 2-to-1 ratio if they only have a specific subset of class abilities? Something else?
 

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Sacrosanct

Legend
Publisher
I haven't really spent any time really evaluating the correlations, but as a hunch when I glance over them, it almost seems like a 3 to 1 ratio. Which makes sense based on the CR of X = a moderate challenge for a few PCs of X level. Theoretically anyway.
 

Rhenny

Adventurer
It feels like more than a 1:1 ratio, but it's hard to say because the overall power of class features synergize differently depending on the base creature. Adding 1 level of barbarian to a kobold may make it a bit more hearty when it rages, but adding the same level to a creature that has more hit points to begin with (an ogre) would make the rage much more powerful (effectively doubling hp vs weapon attacks).
 
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Xeviat

Community Supporter
Supporter
There is no math. Different classes are going to contribute differently. Rebuild your monster and then run it through the DMG monster CR calculator. A few wizard levels with only offensive spells won't do much to a high level monster, but giving them a few shield spells will functionally increase their AC and be a pretty big deal, for instance.


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Rhenny

Adventurer
There is no math. Different classes are going to contribute differently. Rebuild your monster and then run it through the DMG monster CR calculator. A few wizard levels with only offensive spells won't do much to a high level monster, but giving them a few shield spells will functionally increase their AC and be a pretty big deal, for instance.


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Definitely. Imagine shield on a creature that already can take a few hits, or counterspell on a creature that's got a few rounds worth of life and multi-attack.

If a creature with a rechargeable attack, like a dragon's breath weapon, can survive a few more rounds because it has class levels, the results could be devistating when the breath weapon recharges. In this case a few levels in a class will be worth quite a lot.
 

Igfig

Explorer
I third Xeviat's point that there's no direct correspondence between level and CR, and add another important point of my own:

Don't give a monster or NPC the full benefits of being in a class. Instead, give them that class's one or two most archetypal, recognizable features, and ignore anything else that would need its own Action or Trait line. Maybe add a few more hit dice (of the same size as they already have) if you need them to be tougher. Don't make the creature more complex to run than you have to; most of the features add details that you don't really need to care about on a monster.

For example, if you want to give a monster fighter levels, you should give them Combat Superiority (probably the most recognizably fighter-y feature they have), and ignore the rest: second wind, action surge, fighting style, etc.
Or if you want to give a monster wizard levels, give it the Spellcasting feature at an appropriate level (up to however many hit dice it has) and nothing else. If you really want to stress that it's a specific school of wizard, give it the most interesting feature from that school, and ignore the rest.
 

Quickleaf

Legend
I'm gearing up to run a new campaign, and I plan on adding class levels to various humanoid creatures. Thing is, I'm not sure how much that affects their CR. Some of the NPC casters in Volo's guide and the MM have caster levels well above their challenge rating.

Is it a 1-to-1 ratio if they have full class abilities and a 2-to-1 ratio if they only have a specific subset of class abilities? Something else?

A *very* rough rule-of-thumb (see my caveat below) is that:

1/3 of non-caster level = CR
1/2 of caster level = CR

However, if you're familiar with 3e's level-based CR for NPCs you need to jettison that thinking in 5e. Calculating a monster's CR in 5e requires determining a defensive CR and an offensive CR, then averaging the two. This involves DPR calculations.

What this means is you could design a caster with great utility/exploration magic but who is lacking in defensive & offensive magic and so wouldn't follow my rule-of-thumb at all. Similarly, you could optimize a non-caster with feats, high ability scores, and magic items and it wouldn't follow my rule-of-thumb at all.

My approach for adding "class abilities" to monsters is a lot looser than what someone familiar with 3e might be used to.
  • I determine the rough level of the monster's class, revising its HD/HP accordingly.
  • I look through any especially fiddly class abilities and cut them out entirely. As DM I've got enough on my plate so I don't want monsters to involve nitty details like Second Wind or Arcane Recovery.
  • I then recalculate the monster's CR from the ground up as if it were a new monster entirely.

Anything else is IMO guesstimating.
 

Xeviat

Community Supporter
Supporter
Don't give a monster or NPC the full benefits of being in a class. Instead, give them that class's one or two most archetypal, recognizable features, and ignore anything else that would need its own Action or Trait line. Maybe add a few more hit dice (of the same size as they already have) if you need them to be tougher. Don't make the creature more complex to run than you have to; most of the features add details that you don't really need to care about on a monster.

For example, if you want to give a monster fighter levels, you should give them Combat Superiority (probably the most recognizably fighter-y feature they have), and ignore the rest: second wind, action surge, fighting style, etc.
Or if you want to give a monster wizard levels, give it the Spellcasting feature at an appropriate level (up to however many hit dice it has) and nothing else. If you really want to stress that it's a specific school of wizard, give it the most interesting feature from that school, and ignore the rest.

I say give them what abilities you want to deal with. Since you're going to factor them into the CR anyway, give them what you want. Like I wouldn't give Combat Superiority over second wind, actions urge, and fighting style; combat superiority is a subclass ability, and is no more core to the fighter is than eldritch knight spells are. But I have given combat superiority to NPC warriors (The Bladebearer Hobgoblins from Red Hand of Doom for instance).

But, you'll see many abilities in the MM that "almost" mimic some of these things. "Parry", on many of the NPCs, kind of mimics the battle master's parry ... more specifically the defensive duelist feat. Those types of abilities may be less fiddly than giving an NPC actual Superiority (or Sorcerer) dice.
 

MostlyDm

Explorer
Xeviat already hit the nail on the head: There is no ratio. At all. It's entirely dependent on how their class levels change where they fall on the CR calculator in the DMG.

Also, bear in mind: CR, in general, does not take versatility into account. At all. Not even a little. Seriously.

CR only cares about damage and HP, and to hit and defense insofar as those directly affect damage and HP.

So, for example, if you add casting abilities to a monster, but it has no spells that directly deal or mitigate damage... misty step, charm, see invisibility, fly, etc... the CR may even stay exactly the same.

I said this in a different thread:
In general, CR is not really a representative of how difficult a monster is going to be to fight. I think it's mostly just an expression of whether or not the monster is able to do so much damage that a single lucky turn or two could start killing people (or has so much AC and HP that low level parties will struggle to bring him down in 5 rounds). That's why, right there in the DMG, they basically write off tons of things that add huge amounts of versatility to a monster as being irrelevant to CR... like speed, stealth, teleportation, ranged attacks, etc.

Read more: http://www.enworld.org/forum/showth...Boring-quot-Monsters-Ogre/page6#ixzz4V7ClafOL

If you add spells and, for example, now they can Cone of Cold twice in a combat, there's a good chance that will change the damage expression in the CR calculator, so their CR will increase.

All that said, presumably your goal in adding versatility is to make the fight more challenging. So, you probably want to increase the CR regardless, to represent that. After all, you know you're going to use the versatility, whereas for MM monsters the designers can't know how much a particular DM will do so.

In such cases, I think it makes sense to at least increase the CR by +1 or +2. That's what I generally do, at least.
 

The defensive CR will increase by 1 for every 15 hit points. Assuming a 12 Constitution, for a wizard that will be 3 levels, while a fighter would be 2 levels.
So that's easy.

Offensive CR increase by 1 for every additional 5 points of damage. Every other level of a spellcasting class will do that, by gaining a new spell level. Or ever four levels of a 1/2 spellcasting class.
Every other class will vary based on how many levels are added.

For example, one level of fighter is a huge just to damage (Action Surge), but a small boost to hp. (+1 CR... if not +2 or more) Three more levels of fighter is moderate, and unlikely to increase damage that much. (Total of +2 CR) A fifth level of higher is another huge spike. (+3 CR easy). Arguably levels 6-10 are barely a CR bump, only offering hit points. (+4 CR at around level 9) and another jump to damage at level 11 (+5 CR).
 

Caliban

Rules Monkey
Thanks a lot for the advice, it's really helpful. Modifying monsters in this edition seems to be a bit more fiddly than it was in 3e.
 

Xeviat

Community Supporter
Supporter
Thanks a lot for the advice, it's really helpful. Modifying monsters in this edition seems to be a bit more fiddly than it was in 3e.

I find it easier. 3E lied to you and said +1 level was +1 CR. 1 wizard level on a stone giant likely wouldn't have done much, especially if you didn't choose defensive spells. Give it a try. 5E's CR system gives you a good idea of what you're getting yourself into. It's not perfect but it's pretty good.


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S

Sunseeker

Guest
A PCs strength comes from it's ability synergy with other classes and ability utility. Some classes are still superior to others. IE: 5 level 5 Clerics are going to be superior to 5 level 5 Fighters due to their versatility and synergy with each other.

On average, I typically treat 1 class level as +1/2 CR. However, this is an average usually based on the obvious fact that certain class levels provide greater features than others. Adding one level of Fighter to a Kobold will not, IMO add +1/2 CR, however adding 6 levels of Fighter to a Kobold dramatically increases it's challenge (extra attacks, way more HP, fighting styles, etc...) the same is applicable to the rest of the classes. Is a 20th level human a CR 10? Probably more like a CR 12, depending on the class and the base race and how well the DM plays it. It's not an exact science (which is why CR NEVER should have been brought back in the first place!).

But still, I find a +1/2 CR to be on average the appropriate challenge increase at least for adding levels 3-10 (which is where, IMO, we need more "regular" enemies). I've only ever added 20 class levels to a monster and that was when I created my Dragon Lords, which I thoroughly terrified my party with.
 

guachi

Adventurer
I created a 6th level cleric for an adventure I converted from 1e and I gave him a CR of 3. So that fits the rough guide of 1/2 CR per level. Given the encounter favors the bad guy cleric with him having a spell or two already cast when the encounter begins I felt CR3 was fair. Though I intentionally didn't give the cleric spiritual guardian as a spell as that would likely wipe out the party.

If the NPC were a solo rogue I'd likely give him a really low CR, for example, as he'd have a problem getting Sneak Attack off and rogues (at least non-AT rogues) shine with so many of their abilities not triggering off of a short or long rest so a single solo encounter would leave them really weak.
 

Igfig

Explorer
I say give them what abilities you want to deal with. Since you're going to factor them into the CR anyway, give them what you want. Like I wouldn't give Combat Superiority over second wind, actions urge, and fighting style; combat superiority is a subclass ability, and is no more core to the fighter is than eldritch knight spells are. But I have given combat superiority to NPC warriors (The Bladebearer Hobgoblins from Red Hand of Doom for instance).
Good point. I should have specified that a class's "most iconic feature" is an entirely subjective matter; whatever you think is the most significant feature from that class is the feature you should put on it.

But, you'll see many abilities in the MM that "almost" mimic some of these things. "Parry", on many of the NPCs, kind of mimics the battle master's parry ... more specifically the defensive duelist feat. Those types of abilities may be less fiddly than giving an NPC actual Superiority (or Sorcerer) dice.
Also a good point. Combat Superiority, or other abilities with a specific number of uses and/or a range of effects to choose from, are definitely worth simplifying. For instance, when I make a monk NPC, instead of tracking Ki I just let them make Flurry-style attacks as a bonus action, and don't worry about tracking Ki or using the other Ki abilities.
 

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