by Mike Shea on 10 August 2020
Note, this article has been updated from the original posted in February 2016.
When improvising an NPC or custom monster during the game, you can often start with a base DC between 10 (easy) and 20 (hard). If you end up needing combat statistics for your NPC or monster, grab the closest stat block from the Monster Manual and reskin it for flavor. If you want some quick creature statistics, try out the following formulas (round down):
Monte Cook, designer of the third edition of D&D and the Numenera roleplaying game, wrote an interesting article called PCs versus NPCs in which he discusses the time we often waste putting together statistics for NPCs. These non-playing characters (NPCs), he argues, just show up, talk for a bit, and disappear forever. Here's an excerpt:
NPC (and creature) detail is one of the ways in which designers and GMs are often forced to waste a lot of time. That's because the game has all these great rules for fleshing out PCs and making them cool and interesting. A game that explores how well a PC is at combat, at interaction, at a wide variety of skills and actions, and makes all those things equally interesting is a great game. But then, it comes time to make NPCs.
Monte argues that the details our game needs for player characters to stay interesting doesn't apply to NPCs or monsters. Often some quick statistics are all we need to run most NPCs and monsters. Numenera and the Cypher RPG system has an easy way to manage this. A creature in Cypher only needs a level. The rest of the monster's statistics can be easily generated from this single number between 1 (easy) and 10 (very hard).
5e's design won't let us design a system as simple the one in the Cypher system for combatant NPCs. Monsters in D&D have a lot of crunch to them with six attributes, hit points, armor classes, saving throws, attack scores and detailed attacks. Luckily we have the Monster Manual to handle all of this for us.
At its core, D&D 5e comes down to rolling a die, adding a modifier, and checking it against a difficulty check (DC). In just about any interaction that has a challenge, the DC is all we really need to come up with between a range of 10 (easy) and 20 (hard). Anything below 10 we can assume the characters just do without a check. Anything above 20 is likely too hard unless they're picking the doors to Lolth's vaults in the Demonweb Pits.
When a PC wants to interact with an NPC in some way that might be challenging for example being diplomatic, lying their asses off, or threatening them; all we need to do is ask ourselves "on a scale of 10 to 20, how difficult is this?". The answer to that question is our DC check.
Any particular NPC may have strengths or weaknesses when dealing with the PC. Maybe they're not very easy to intimidate (DC 16) but might succumb to flattery (DC 11).
Coming up with DCs for interactions with NPCs isn't too hard, but what about combat? Again, we can't have a system as easy as the Cypher System for this. Instead, we can choose one of two systems that still make it very easy.
First, use the NPC statistics in the back of the Monster Manual. We might be tempted to build new stat blocks or determine that the NPC stat blocks don't fit the NPC we have. Most of the time, though, it really doesn't matter. Choose the closest stat block that fits and go with it. If we need some higher power NPC stat blocks or more variety, we can use the NPCs from Volo's Guide to Monsters. For spellcasters, feel free to change up their spell lineup to fit the new NPC you've created.
If for some reason one of those stat blocks won't do, we can reskin a monster stat block from the Monster Manual into something closer to what we want or need. For example, if we want a barbarian warlord who hits like a freight train, we might use the fire giant stat block for the warlord.
Reskinning stat blocks is the most powerful improvisational tool for D&D.
The section "Monster Statistics by Challenge Rating" from chapter 9 of the Dungeon Master's Guide has statistics you can use to build a quick NPC or monster on the fly. For a looser and easier system, consider the following baseline statistics. First, choose a challenge level for your NPC or monsters. Consider that a single monster of a given challenge rating is roughly equivalant to four characters of that level. Use the following formulas to determine the rest of a creature's statistics:
That's about all you need to build a quick NPC stat block if you'd rather not look up a stat block in the Monster Manual. It's definitely a loose system and not perfectly matched to the math of 5e D&D but the whole challenge rating system is likewise imperfect. In particular, it doesn't work well for monsters below CR 1 although just using the baseline stats would work (AC 12, +3 attacks and saves, 15 HP and 5 damage). Still, this will get the job done in a pinch.
You are, of course, encouraged to tweak the results of the above formulas to fit the specific monster. Just don't spend too much time on it.
For a better and more useful look at generating monster statistics on the fly, check out 5e monster manual on a business card including this really useful single-page PDF for selecting monster stats at any challenge rating.
Its easy for us to complicate our lives without thinking about what we're doing. It's comfortable to worry more about monster statistics than the more open and creative components of our D&D games. The truth is, monster and NPC statistics just don't matter that much. Reskinning a stat block from the Monster Manual saves us a ton of time and, 99 times out of 100, works just as well as custom building a monster from scratch.
Keep the tools on hand that you need to improvise a great game. Start with a DC between 10 and 20 based on the situation and, if you need to, reskin a stat block from the Monster Manual. It's the easiest and most powerful way to run NPCs at the table.
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