Dragon Encounters

Making dnd combat fun, finding monsters that fit together, monster tactics and strategies, and other ways of using the monsters of dungeons and dragons

DOPPELGANGER: The Impersonator That Accuses Itself

How to Use – Social Encounter


Combat rating 4


1 Doppelganger (CR 3)

3 Cockatrices (CR 1/2)


Combat rating 4


1 Doppelganger (CR 3)

2 Flying swords (CR 1/2)

1 Rug of smothering (CR 2)


Combat rating 6


2 Doppelgangers (CR 3)

2 Mimics (CR 2)


Combat rating 7


1 Doppelganger (CR 3)

1 Druid (CR 2)

2 Knights (CR 3)

1 Priest (CR 2)

1 Scout (CR 1/2)

When building an encounter using a doppelganger, you will be better served by building a short encounter rather than an entire storyline. Build a long storyline, and you might end up with a doppelganger who gets exposed when you’ve barely started. Or, you might reach the part where your players are supposed to solve the mystery, only to find out that they have no idea how to solve it.

By building a short encounter, you leave the stakes low enough that you can afford both to let the players lose and to lose yourself. If the players lose, you can always bring the doppelganger back. Repeat villains are a lot of fun, so long as the villain escapes fairly. (The other way raises resentment, and makes the players’ decisions not matter.)

With luck, your doppelganger can be a repeat villain, who shows up every so often to try to kill the PCs (as an example. I’ll provide a few ideas below.) After failing, the doppelganger retreats, only to show up later and try again. I’ll also provide ideas for diverting suspicion, for making an escape, and one or two ideas for once the doppelganger is caught.

That said, if your doppelganger fails on his first try, you can have the villain control a number of doppelgangers. They are one of the few monsters which it makes sense to send out one at a time.

(In general, building your campaign out of a list of short ideas is a much better idea than plotting out a long campaign. It makes your game much more flexible. But it’s doubly important for mysteries.)

I’m going to go through the main aspects of a doppelganger type mystery, rather than writing a single non-combat encounter. You should be able to put them together into a proper encounter without trouble.

  1. NPC Suspects

The first thing any mystery needs is a list of possible suspects. This is obviously especially necessary with a doppelganger, where its entire modus operando is to imitate someone else. Building a useful NPC requires the following items:

  1. A memorable feature. This can be a personality quirk, a funny way of talking, perhaps a strange name or a tendency to stir up a specific type of trouble. My favorite way is to take 1-2 of the traits/ideals/bonds/flaws from the background section of the Player’s Handbook, and dial it up all the way.
  2. A reason why the players want/need to interact with them. Giving them a single skill, and finding ways to have the players need it is a good way, providing you only use skills that the players themselves don’t have. (If not, you risk overshadowing the players.) Tool proficiencies, non-combat spells and abilities, connections to certain segments of the population all work, subject to the same conditions. So does having them being the ones to hire the PCs.
  3. Some reason for them to be in this area, and interacting with the PCs. Sometimes this doesn’t need doing, but you should remember to think about it in advance. Aside from causing plot holes if not done, this is going to give you a way to actually use them in the first place. (Leaving it up to the PCs to interact with them will end with half of them being written off, right out of the door.)

Optional (not necessary, but makes it interesting, if you think you can manage it.)

  • A secret that they’re keeping from the players. This can be that they’re engaged in a minor crime, such as minor theft or smuggling, it can be a crush or hate for another NPC, or it can be that they’re the child of one of the players’ defeated enemies. This increases the story, by giving more to find out, but also makes stuff a lot more complicated. Be prepared to pull out a reveal if you find that it’s confusing people too much.
  • A feeling/relationship with another NPC. (There are dozens of different types of relationships, both positive and negative. Romance is actually one of the worst choices, as people often keep it under wraps.) Again, this can make stuff interesting, particularly in a story with an impersonator, and it can help flesh out the world, but it’s hardly necessary. If it’s going to slow stuff down or mess up the story, don’t include it.
  • Plots, or Doppelganger Goals

This is ideas for what the doppelganger might be trying to do, and how to go about it.

  • Trying to kill the PCs. Don’t use poison, as this is hard to prevent, and just results in the players taking damage and/or debuffs, which won’t be popular. Instead, have the doppelganger set up encounters and/or traps. Encounters can be done by having it open doors so the monsters can get in, getting them in trouble with local crooks or authorities, and sending the PCs in the wrong direction. Traps are best done by locking them in while setting the house on fire, or collapsing a hill on them at the worst time for them.
  • Trying to steal from them. This is tricky, because they’ll really resent it. I would have the doppelganger target quest objects, and make sure that the doppelganger succeeding will slows them down but not defeat them, even without them recovering the items. Basically, figure out what you can afford to let the doppelganger steal before it tries, so you don’t end up in a situation you can’t handle.
  • Finding out information from them. This information will then be used to set up traps and ambushes for them, or to remove the quest objectives before they can get to them. You’ll need a quest that sends them to a lot of different places for this to work, and you’ll need a way for the doppelganger to figure it out when spying. If the players have a map, or if they have to make some preparations beforehand that the doppelganger can discover, those might work.
  • You can also have the doppelganger be after someone else. Perhaps it’s someone they promised to protect, perhaps that person has something useful to them that the doppelganger is trying to steal. Perhaps the doppelganger is running a scam, and the players have a chance to expose it. I would avoid having it be trying to kill an NPC, as having it succeed at that would be unappealing. Don’t have it be trying to do something you don’t dare let succeed.

Ways for the doppelganger to get caught

The next thing needed in a mystery is mistakes the doppelganger can make, to give the players clues. You’ll have to make these clues more significant than in a standard mystery, and I still don’t really expect them to get it. In the next section I’ll give moves that the doppelganger might use to divert suspicion, and those are more likely to let them catch it, as they let the players know that something is wrong. Still, it wouldn’t be a proper mystery without clues.

  • The obvious one is that the doppelganger acts in some way that the NPC would never do. This requires that they met the NPC before, of course. As per making it noticeable, don’t just have the vegetarian eat a meat dish, have them be upset that the inn doesn’t have steak available, and argue with the players about finding a new inn.
  • A variant is where the doppelganger shows capabilities that the NPC wouldn’t have, such as acts more spry than the elderly or out-of-shape NPC would, or more mature than a young NPC should. (Just make sure you don’t do this when the doppelganger isn’t imitating them, if you want to use it.)
  • The opposite also works, as in when the doppelganger reveals something that the real NPC should not now. (This assumes that they’ve dealt with this doppelganger before, and as such it knows some stuff about them.) This can be PC abilities, or dangers specific to the villain (assuming a constant villain, with at least some consistent capabilities/methods.) Like before, you need to make a deal of it. One way is if it suggests a course of action (wise or not), and bases its reason on this knowledge.
  • If they have capabilities that the doppelganger doesn’t have, the doppelganger will have to bluff, or figure out means of concealing its lack of skill. So long as the PCs don’t ask it to use its [nonexistent] skill, it won’t draw attention to it. If you want to make that a clue, make certain that the ability has been used before the doppelganger started impersonating the NPC, preferably recently, more than once, and in a significant way.
  • If/when the players request the skill, the doppelganger can either give a reason why not, can pretend to do it [assuming divination magic or a knowledge skill, that has no visible effect,] or can find an excuse to get out of eyesight first, and then run for it.
  • If you have access to mystery short stories, take a look through them. Many are solved through these types of mistakes, and you should be able to draw inspiration from them. (Although you’ll have to make the mistake a thousand times more obvious. If the solution involves any actual knowledge, make certain to drop that knowledge into the game beforehand, even if your players should know it, and try to do it in a way that makes a difference to the game. If you can’t manage that, skip this suggestion.)

Any and all of these stand a chance of the players realizing that the NPC is acting out of character, not realizing that it’s an imposter, and asking it about its behavior. Have ideas for excuses/bluffs ready. The excuse or bluff should be only so-so convincing, enough that the players can realize better if they think about it, but not so bad as to be ridiculous.

Doppelganger distractions

These are ways that the doppelganger can try to mislead the players, by causing them to suspect someone else. (Strategy wise, they’re probably a mistake. They are too likely to backfire, arousing the players’ attention to the possibility of a doppelganger in their midst while accomplishing little or nothing of value for the doppelganger, but they are also fun.) 

Be aware that they add complexity. If your players prefer straight up combat over complicated plots, you might not want to use them. Alternatively, use them, but be prepared to have your players skip right past them in pursuit of the “real” plot.

  • The simplest, and most obvious, is to beat the other NPCs to the punch. Accuse a different NPC of being a doppelganger, or of some other crime, and make certain that he/she isn’t around to defend himself/herself. This can be accomplished by waiting for an opportunity, decoying them elsewhere, or tying them up / murdering them. Their absence can be made into proof of their guilt. (This is probably the first one you’ll use, then the others are more complicated versions.)
  • The doppelganger, in addition to having a fixed identity that he uses as a disguise, also imitates another (or more than one other) NPC. If it acts somewhat suspicious, but not enough for the players to openly accuse the other NPC of being the doppelganger, it will shift guilt quite convincingly. Even if they do accuse the NPC openly, giving them a chance to deny it, attention might be diverted.
  • The doppelganger arranges that multiple NPCs are all coming with stories of having seen each other acting suspiciously, or being in a location where they shouldn’t have been. In reality, they each saw the doppelganger, using a different guise each time. There are two possible solution methods [choose one.] The more basic is that they all have alibies, once the PCs investigate the matter, except the one that is the doppelganger’s main guise (because that one can’t be in two different places at once.) Alternatively, each NPC’s story reveals something about the doppelganger’s objective, except the one that is told to them by the doppelganger.
  • Instead of letting itself be seen in another form, the doppelganger plants evidence against one of the NPCs. If they were hiding a secret in the first place this will be even more convincing.

Doppelganger Escape Strategies

These are methods the doppelganger might use to make an exit, (or that you might have him move, to make his exit more exciting). The idea behind all of them is to confuse/delay the PCs just long enough for him to reach a crowd, at which point the doppelganger is impossible to catch.

  • The doppelganger adopts the guise of a friendly NPC guard, and tells the PCs to finish off the doppelganger’s allies (if using) or the threat the doppelganger created (such as setting a fire, releasing dangerous beasts, etc.’) and he’ll take down the doppelganger. Alternatively, if the nearby NPCs aren’t fighters, he uses the disguise to run screaming from the threat he created.
  • The doppelganger retreats into a nearby room. When they pursue, he adopts the guise of a cowering civilian who tells the PCs that the doppelganger just ran past.
  • The doppelganger takes the guise of a civilian, spills a flask of blood, lies down in the blood, and pretends to be a corpse. If applicable, you can add the corpses of some civilians who were in the room and whom the doppelganger killed before playing dead himself.
  • Two versions of the same NPC are in the room along with a monster. both of them scream and run in different directions.
  • The doppelganger takes the guise of the mayor, or other important noble, and order the guards the arrest the PCs for trying to kill him. Alternatively, the doppelganger imitates the mayor’s wife or child, and throws itself into the mayor’s arms for safety.
  • Should the PCs split up, with some of them going in pursuit and the others finishing up behind, or with them splitting up to search two areas, you can slip a player who isn’t in the doppelganger’s area a note telling him that the doppelganger is using his form, and maybe a line or two about the doppelganger’s objective. Choose a player who will enjoy such a charade, and let him decide on the doppelganger’s actions.

Using the doppelganger as an ally

Another interesting way to use the doppelganger might be as an ally of the PCs. Doing so would probably require a plot based around NPC interaction, and goals that need to be accomplished in a secretly. (Decide before trying whether such a plot will work for your game group. Many players dislike having to be subtle. If you do run such a plot, you’ll probably want to have it be a 1-2 session interlude between more typical games.)

You could supply the doppelganger straight out by having the NPC quest giver tell the players that he’s sending a doppelganger to help them, or by having the doppelganger offer his services for hire. Alternatively, you could have the doppelganger be working on his own as a crook, and when the players discover him, he offers a deal where he helps and they don’t expose him. If he was working for the villain, maybe he’ll offer his services in exchange for his life.

(Ideally, the players would be the ones to offer him leniency in exchange for help, but if they think to do so it won’t be in a situation where you were actually planning on using the doppelganger like this. That said, if you can roll with it, you might have a very interesting game as a result/reward.)

When taking this approach, I would suggest that you limit how much the players can trust the doppelganger. If the doppelganger was originally a crook or an enemy, this will happen naturally. (You should also not forget that he can betray them, and will if it suits his interests.) Otherwise, you might want to make the doppelganger be lazy, or cowardly, or find some other reason that they can’t give him too much slack. If not, he becomes too useful, and will overshadow the PCs, especially any with a rogue class.

(With deficiencies, you can use him together with a rogue class. He’ll be a tool that they can use to sneak in, but they’ll still need the rogue to sneak in also as they can’t trust the doppelganger. Their strengths and weaknesses will complement each other.)

Having finished exploring the social part of using a doppelganger, we are finally up to –

Combat Encounter 1 (difficulty 4 [ideal difficulty level])

Until now, I’ve mostly been having the doppelganger imitate NPCs. Using a doppelganger in combat requires using it to imitate the PCs. This creates a whole range of problems.

When imitating a PC, you aren’t going to be able to run the monster. You can run it when it’s imitating an NPC, as both the NPC and the impersonator are run by you, but you don’t have a chance of imitating a PC unless you happen to be a doppelganger yourself, in real life. Your players will notice who is speaking, and find it pretty easy to deduce which one must be the real PC.

Literally the only solution is to ask the player who normally runs the PC to run the doppelganger as well, and hope that he’s willing to do a good job. With this in mind, my first and foremost criteria in choosing who to have the doppelganger imitate is who will be interested in playing for the other side, and possibly messing up the other players. (At the same time, be aware of stress potential within the group. How likely is this to tick off other players, and by how much.)

In the same vein, I would give the player a high degree of autonomy over how he plays the doppelganger, with the reasoning that it’s more important that it be played well than that it be played the way you envisioned it, and that having autonomy will increase his enthusiasm for playing it well. I would even go so far as to tell him that all further instructions should be treated as suggestions, which he can choose to ignore.

With that covered, let’s look at the ideal roles for a doppelganger in a combat situation.

Option 1: Have the doppelganger start off as imitating a high-priority target, such as a spellcaster. (He should not imitate the highest priority type target, such as a dungeon boss, as that will get him killed within a round when the players concentrate all their ranged attacks and spells on him.)

Pretending to be a spellcaster will make it likely that one or more melee PCs will charge him, at which point he can take their form. Since it makes perfect sense that the melee PC won’t stay around, now that the spellcaster has shown itself to be a low priority doppelganger, the doppelganger can now either move toward another mage on its own side, or retreat back to the player mages, to “Protect” them.

The player playing the melee PC should be informed that he’s now playing two roles, his own and the doppelganger’s, and that each of his two characters should accuse the other of being the impersonator. You might also give the doppelganger a special ability, namely that it gets to move on the same initiative as the PC it’s impersonating.

(The reason you don’t want to have it imitating a melee fighter is that it won’t affect combat strategies at all while in melee form, that when it seeks to imitate a PC its only choices will be frontline melee PCs, and that it won’t be able to go anywhere useful without giving itself away. The PCs came to deal with a threat, and the fact that the guard turned out to be a doppelganger isn’t a reason to change plans. So, either the doppelganger goes with them, which is not where it wants to be, or it zeroes in on the vulnerable PCs and gives itself away immediately.)

Option 2: The doppelganger waits in hiding until the battle begins, then it emerges in the guise of one of the vulnerable, spellcaster PCs and attacks its double.

The spellcaster obviously knows who it is, but every other PC should not be able to tell. Even if they figure out at one point, such as when the spellcaster casts a spell (the doppelganger can’t cast spells), they won’t be able to keep track of which is which, especially if the doppelganger moves around the real PC.

Most spellcasters aren’t optimized to take on a single opponent, and even if they are, that will take their focus away from the rest of the battle. Similarly, any melee could separate the doppelganger from its double, but that will occupy them for several rounds during which they’re needed elsewhere. The doppelganger in this scenario is half threat, half distraction, and for roleplay throw in accusations made by the doppelganger accusing the real player of being the fake one.

(Ideally, ask the player to make the accusations. Then you can have the player playing both sides, and accusing and defending himself at once. Again, this needs the right player, but if you have such a player, it’s wonderful.)

Combat Encounter 2: (difficulty 5)

The other way to use a doppelganger go sow confusion is in combination with traps.

When using this approach, I would suggest several levers, probably 2-3, that adjust how the trap functions. The idea is that one of the traps is always functioning, but which trap effect will change depending on which lever was pulled last.

If you like, you could have the traps be set so that leaving the same one on for too long is extremely deadly, that each time a trap is activated it becomes a little bit more deadly, or that the same lever needs a few rounds before it can be pulled again. The first two ways force the players to be constantly switching between different traps, the last means that they can’t just station a range attacker or spellcaster near a lever to pull it when necessary.

(You might not want to use more than one, or maybe two, of those conditions to the same setup. Make stuff too complicated and your game will bog down, as the focus will go from trying to beat the setup to trying to remember the setup.) For its part, the doppelganger can switch traps at the worst possible time for the players. It can also use their face to make them think that it’s about to switch traps, then not do so.

 I would also use a number of enemies, so that there is a fight going on at the same time. The battle is so that the players’ focus is split, as taking out the doppelganger will be fairly easy if they can focus on a single goal (the difficulty added by traps is repetitive, predictable. The traps won’t be enough of a distraction by themselves unless you make their effects extremely complicated or extremely deadly. Extremally deadly means that the doppelganger might end up killing one or two of the PCs, and/or that you’ll handicap yourself trying to keep the encounter fair. Extremally complicated is never a good idea, under virtually any circumstances.)

Different types of traps that can be used include any of the following:

  1. Traps that shoot acid, darts, fire, or lightning along predetermined radius. You probably want two-three zones that will be affected, and to have the trap always activate at initiative 20. That way, the goal is not to remain on the areas at the end of their turn. Alternatively, the trap activates when a PC steps in front of it, and they have to make a DEX save to see if they can escape it.

Escalation will consist of the affected radius getting larger, and/or the DEX save DC going up as the trap gets faster. Fire and acid can also heat up or fill up the room if they activate too often, for too long.

  • Water pouring down and filling up the room. The first round, only the site of the waterfall(s) is a problem. Then, it becomes harder to move, harder to fight, and finally hard go breathe.
  • Traps that effect movement. A trap that releases a strong wind, like in the Gust of Wind spell, for example. Or the floor could tilt, or become slippery, or open up in places (like trapdoors.)

For added difficulty, put pits with spikes at some (or all) edges of the room that the traps or pushing them into. (If you want, you could have the pit’s area extend a little every round, thereby slowly reducing the size of the battle area and giving a timer.)

For multiple traps, have the Gust of Wind, the room’s tilt, come from different directions.

For intensification, either have the tilt of wind increase, so that if the switches aren’t flipped every few turns the floor will go vertical, or the wind will have the force of a hurricane.

  • Sliding walls. Either affecting the entire area, and threatening to squash the PCs if it goes too far, or sliding across the middle of the dungeon to separate them from each other.  You can also decide if the walls return to their original position instantly, or at the same speed in which they moved out in the first place.

Leave a Reply

Your email address will not be published. Required fields are marked *

About Me

I have been a DM for several years, and I was designing home RPG games since my young childhood. I have been a fan of many different types of games (computer, board, RPG, and more) and have designed several for my own entertainment. This is my first attempt to produce game content for a wider audience.