by Mike Shea on 26 June 2017
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:
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.
Non-combat NPCs, however, don't usually need all that stuff. We rarely end up in combat with most NPCs in the game and thus don't need a full range of combat statistics. Often all we need is a name and a difficulty class based on the situation between 10 (easy) and 20 (hard).
No NPC can exist without a good name. A solid name generator might be the most important tool for the Lazy DM. Whatever your method to find a good name, once we have it, we must write it down. We have no idea which NPC is going to come back again or turn into a major part of the story and the solidity of our world falls apart when our players realize even we don't remember their names.
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).
Another technique, even easier than making up a DC beforehand, is to ask the player to roll a check and then, from the result, tell them what happens. This gets into the idea that there aren't just successes and failures but shades of gray. Someone who rolls really well may get something more than someone who just rolls in the middle. Someone who rolls a 1 might bring some hilarity to the situation or fail forward into a new and interesting direction in the story.
When you're basing the results of an interaction on an arbitrary roll like this, focus on the total result and not just the die roll. If someone rolls a 2 but happens to be +12 to that particular skill, they might be clumsy about it but will still get the job done. Players want to feel empowered by the training they have in particular skills so even if their roll sucks, that power should be accounted for in the narrative.
The best thing about this "roll and tell me what you get" approach is that there is no math involved at all. It's even easier than Monte Cook's cypher system.
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. It will still get the job done.
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.
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.