The doppelgänger is a weird creature, even amidst all the bear-owls and the giant but deadly cubes of gelatin. If you weren’t aware, a doppelgänger is a creature that wants to kill you and take over your life. It is said that doppelgänger infestations can go unnoticed for years. In some kingdoms, every member of the royal line and all the courtiers have been replaced by doppelgängers, each unbeknownst to their fellows. Doppelgängers were introduced a bit later, but still relatively early in D&D history, in E. G. Gygax’s Greyhawk supplement to the game. If you were hoping for a whole deep dive on doppelgängers through the ages, this is not that because Dump Stat Adventures already wrote that blogpost. Instead, this is a bit of advice and best practices for running doppelgängers.

Sometimes players encounter already-transformed doppelgängers. In such situations, the players may benefit if they can deduce that the person they are interacting with is a shapeshifter. There isn’t much advice I can impart here that wasn’t already covered in my post on how to run mysteries, but please indulge me as I tell you a humorous tale. I once ran a dungeon located in Ribcage, a city on the edge of hell itself. One room in this dungeon included an important NPC, but that important NPC was bound, gagged and nearly dead in their closet, while a doppelgänger imitating the NPC did their best impression of an arch-devil’s vizier. My players had no idea that this was the case but did have enough information to know that they were about to enter the vizier’s personal chambers. One player had recently gained some shape-changing spell and transformed themselves into a young, opulently-dressed tiefling (the dominant group within the citadel of Ribcage). When they entered the room, the transformed player immediately said “Gram gram!” and proceeded to pretend to be the long-lost granddaughter of this NPC. The doppelgänger meanwhile had no reason to believe this wasn’t actually their granddaughter and both sides played along with this ruse, each thinking it was they who had pulled the wool over the eyes of the other. The reveal, and my players’ reaction, remains a highlight in my game-running career.

“Wait, I thought this post was going to give me advice on running doppelgängers.” I’m getting to it! First I needed to tell a little anecdote to pad out the word count because this blog post isn’t really a blog post, it is a tweet thread disguising itself as a blog post, just like a doppelgänger will disguise itself as a kindly tiefling grandfather. As much fun as the story above was, a doppelgänger’s best use isn’t to pretend to be some NPC that players haven’t met. That makes it much harder to deduce the truth and solve the mystery. The best use is for the doppelgänger to impersonate a player-character. Now they’ve been collecting clues, without knowing it, as long as they’ve know the character. But can they solve the mystery?

A doppelgänger posing as one of the player-characters is a classic trope for a reason: it’s fun. Both the character and the imposter get to try to convince the other characters that they are the real one, and the other players have to figure out which one is telling the truth. It is like a little mini-game in the middle of your dungeon-crawl. And it is a good one too; hidden role games (e.g., werewolf, secret Hitler, or bodies bodies bodies) are beloved staples of the time honored tradition of playing silly games with friends. The fun in this situation, when translated to a roleplaying context, is

1. For the impersonated player to prove that they’re the real one (“please, you have to believe me!”)

2. For the imposter to successfully pull one over on the other players (“hehehe, they’ll never suspect me”)

3. For the other players to solve the mystery of who is the fraud and who is genuine (“elementary, my dear Arneson”)

However, those games are structured to keep everyone but the imposter unaware of who the imposter is. Too often, I’ve seen doppelgängers ran in a way where players can only get the hidden-role-esque thrill if they do their best to forget that obviously the one the referee is playing is the imposter. But it is hard to delude yourself that much. The issue with using this trope with a roleplaying game is that the player character being impersonated is typically played by their player, and the imposter is played by the game master. The other players can try to ignore this metagame information, but it spoils the fun. Metagaming isn’t always a bad thing (some games use it to their advantage, as I describe in this review on the Bones of Contention blog), but in this instance, it deflates the most exciting elements of a doppelgänger encounter.

This method for running doppelgängers preserves the mystery, prevents metagaming, and preserves the fun of the situation. First, when an NPC (such as a doppelgänger) impersonates a player-character, that character’s player will refrain from speaking directly to the group. Instead, they will text the referee (or pass notes if in person; it just needs to be any form of secret communication) describing the words and deeds of their character. The referee will describe the actions of both the impersonated character and their imposter. The other players’ actions will then be solely based on their interpretations of what the two potential imposters say and do, not on which person at the table is saying them.

The fun here is similar to games like Taboo or Codenames. In those games, there is a constraint (what types of clues you can give) for the cluegiver. Here, the impersonated player is giving the clues, and the other players are guessing. The constraint here is that the clues are all delivered in-character and that there is an imposter trying to actively subvert the cluegiver and make the players guess incorrectly. When ran this way, a doppelgänger is no nuisance monster—they can be the centerpiece of an entire session and provide much needed variety to busting down doors and fighting orcs.

A caveat to this method: the referee must get affirmative buy-in from the impersonated player either before the game (if they know that it’s likely to happen) or at least before using this mini-game. There are all sorts of reasons a player might not be into this idea, and that is okay! Consent is paramount. But if everyone at the table is on-board, a doppelgänger encounter can be on of the highlights of your game-running career as well.