Building an NPC / Monster

Question

In my game I'm about to introduce a group of Dwarf fighters that will start out friendly to the players but have a pretty good chance of becoming enemies of the PCs. I want them to be a fair amount stronger than the PCs (they are level 5) but not insanely so. I'm struggling to figure out what stats to give them to support that narrative.

After running this game for a while and throwing different combinations of monster CRs at them, I'm getting a decent feel for what is a challenging / deadly fight. They can handle a lot more than I first thought before I realized the difficulties were based on a 4-6 encounter adventuring day.

I've come across two main suggestions for building an NPC / monster like this.

1. take a monster stat block and customize.

2. create a PC

That led me to start comparing pc builds and monster stat blocks. Here it's suggested that an NPC with class levels has a CR equal to ~2/3 of its class levels. So I thought I'd build a 10th level fighter which should be about equivalent to a CR 7. That sounded about right to me. The party would need to work at taking down just one of these guys and a whole group would be completely out of the question.

So I build a level 10 fighter. I gave him splint armor and a shield 19 AC
98 HP
Str +4, Dex +0, Con +4, Int +0, Wis +1, Cha +0
a battleaxe +6 to hit thanks to dueling fighting style with 1d8+4 slashing damage. He'd get two attacks so that would average out to be (4+4) x 2=16 damage per round.

Compare that to the monster stats per CR on DMG pg 274. A CR 7 monster should have:
15 AC
161-175 HP
+6 attack bonus
45-50 damage per round

Defensive
Ok, so 95 HP would be CR 2 / AC 13. The AC is off by 4. Per the guidelines, adjust the CR up 1 per every two AC difference. That's another 2 AC. Roughly 4 CR defensively. That seems a bit low. 4 CR vs the 7 CR I was going for.

Offensive
16 damage / round is 2 CR.
2 CR goes with +3 attack bonus but this fighter has +6, a difference of three so I need to add 1.5ish CR. So that ends up being a CR 3 or 4.

Overall My level 10 fighter sounds like a pretty solid CR 4. Not what I was going for. Ok so maybe I just need to boost him up a bit to hit the suggested defensive and offensive stats of a CR 7.

CR 7
15 AC
161-175 HP
+6 Attack bonus
45-50 dmg / round

Ok so +6 attack bonus matches up, good.
15 AC, meh, these guys are a bit better protected, no biggie.
161-175 HP, jeez.. that's quite a bit more HP, but maybe I'll boost it to 130 and split the difference with the AC.

This is where I'm really at a loss - 45-50 dmg / round.
How could a fighter put out that much damage?

Here I see that a Champion Fighter is only going to put out 17 dmg / round at level 10 and only 35 dmg / round at level 20. That doesn't seem right.

A level 20 fighter will only put out as much damage as a CR 5 monster?

I feel like I'm missing some pretty substantial understanding of these mechanics.

How can I build these NPCs to be versatile enough to be an NPC or bad guy and not throw them too far on either side of the power scale?

Answer 1

You have an apples and oranges problem

PCs are optimized to survive and win multiple encounters per day. NPCs are are optimized for one encounter and they are expected to lose.

The spreadsheet you have linked is factoring in hit/miss chances and critical damage - CR calculations don't do that. They assume all attacks hit for average damage and that AoE affect 2 creatures.

• Your 10th level champion has a damage output of:
  2 attacks x ((4.16 x 2) average damage + 5 bonus) = 26.7 x 4 (3 round plus 1 action surge) / 3 rounds = 35.5.

• Your 20th level: 4 x ((4.16 x 2) + 5) x 4 / 3 = 71.

A champion NPC also has Second Wind to increase HPp and +1 to AC from the second fighting style (Defence is the only one that synergizes with TWF). An NPC does not have to save anything for future encounters because, win or lose, there aren't going to be any. For this reason, many PC features do things outside combat - NPC features don't.

Further, a group of PCs of different classes is far more effective than a group of the same class. Imagine your Champion fighter under the effects of Haste (1 extra attack per round), with a d10 bardic inspiration die to turn a miss into a hit, and allowing the Rogue to get sneak attack damage every round.

Answer 2

You are missing some pretty substantial mechanics of the documents you link.

DMG CR calculations ask you to sum the damage a creature is capable of dealing in a round, implicitly assuming everything hits.

The spreadsheet you link presents expected damage, based on some assumptions about target AC. (See the second worksheet, "accuracy".)

In your case, you'll see that the calculated accuracy of the L7 fighter is 55%. Inverting that, you see that the fighter would do ~twice the damage you list.

As for the rest of it...

Once you're interpreting those documents correctly, I think you'll find out numbers work out much closer, and you'll feel like you have a lot more versatility.

That said, no amount of pen-and-paper work will replace actual playtesting, and no amount of "correct" CR figuring will compensate for the combination of tactics, terrain, and cover.

CR is useful for knowing how to describe an enemy going into an encounter. Whether it's a cake-walk or a bloodbath is largely up to how each side plays the hand it's dealt.