It Finally Happened: A Doppelgänger Infiltrated the Party

I've been playing for 31 years and this was the first time a doppleganger infiltrated the party.

Jeremy: “You are now a bat. You are a doppleganger, act like one.” Matt: “Yeah... I also hate you. So was he really a doppleganger in the game or did you just make him one because everyone was paranoid?” Jeremy: “He was totally a doppleganger. And I chose when we went outside who he was going to change into. Moon won the jackpot. I'll get you more information. And, yeah, it would behoove you to murder the bat. Pretending to talk to the bat. Then strike others as well.” Matt: “Really... the bat should have attached the moment he saw that he had been copied Attacked.” Jeremy: “Last night, during the session, I scanned the Polymorph and stopped at 'you gain the mental attributes of the creature' thinking 'Oh, you think you're a bat'. But then I read further this morning 'You still have your memories.'' So, you are correct, you would as the bat have agency. You may play both bat and doppleganger. One challenge, is the bat only has blindsight/echolocation. So I'm not entirely certain how much you'd know what Moon looks like through those senses (at a minimum, lets go with it was disorienting, and the bat is piecing together).”
First text conversations with Matt.

I have played fantasy Role Playing Games (RPGs 🔍) since 1988. In those 31 years, I cannot recall a time in which a doppelgänger infiltrated the player character’s party. In our July 1st 2019 session of Tomb of Annihilation, that changed. I wrote this on July 2nd, 2019, but am holding off on publishing until the campaign is wrapped up.

About 4 sessions prior, the players freed from a mirror of life trapping a cadre of non-player characters.

  • A human champion of the deceased queen
  • A minotaur lieutenant
  • A drow wizard
  • A human rogue

They already had Trevor, a human guard once employeed by the Red Wizards, working with the party. Poor Trevor died to a Bodak. And the minotaur died when the party attempted to move a statue that encased a sphere of annihilation. Alas the poor minotaur fell into the sphere.

They also allied with a twice-liberated now frustrated Dao; They had freed the Dao from a bottle but another trap ensnared it. Again the characters freed the Dao, and it joined forces.

The party also brought into their team an awakened lizard. Octavion, a fastidious lizard had spent quite awhile hiding in a statue. Octavion previously traveled with the human rogue, and the Company of the Yellow Banner. Octavion had managed to read a few books. One on pubs and brewing. A right fine chap this Octavion; Eager to converse and banter.

Based on prior information, the party suspected that somewhere in the dungeon, they might encounter a doppelgänger. They found a journal of one of the members of the Company of the Yellow Banner. The journal suggested that the company may have had a doppelgänger in their midst.

A large number of Non-Player Characters (NPCs 🔍) seeded an environment in which a doppelgänger could bring about some chaos. With the hook set, I waited for the moment when the doppelgänger could strike.

Moon (a Player Character (PC 🔍) Tabaxi ranger/rogue), Erd (a PC dwarf wizard/barbarian), and Pox (an NPC human rogue doppelgänger) choose to explore a secret room. The dungeon then separated this small group from the larger group. In haste, the three explored the rooms beyond, finding treasure, animating guardians, and runes that radiated conjuration magic.

Seeing pending doom, the characters raced for the runes to get out. In that moment, before anyone knew what would happen, I mentally committed to having Pox take the shape of Moon. Pox knew Tlad was eager to gain control, that the Dao was angry, and Octavion may, in its blathering, draw further attention to Pox. I spent time thinking about each NPCs mindset and surface thoughts. Because Pox should know them. I also considered the new trickster god inhabiting Moon—one bent on vengeance against wrong-doers.

They raced to the runes. Pop. Pop. Pop. Teleportation. Better yet, they had chosen one that cast polymorph on the characters. Moon failed its save, and changed into a bat. Erd made its save. And Pox failed its save, but “[polymorph] has no effect on a shapechanger” ( System Reference Document: Fifth Edition (SRD5 🔍)).

Jeremy: “Last night, during the session, I scanned the Polymorph and stopped at 'you gain the mental attributes of the creature' thinking 'Oh, you think you're a bat'. But then I read further this morning 'You still have your memories.' So, you are correct, you would as the bat have agency. You may play both bat and doppleganger. One challenge, is the bat only has blindsight/echolocation. So I'm not entirely certain how much you'd know what Moon looks like through those senses (at a minimum, lets go with it was disorienting, and the bat is piecing together).” Matt: “I mean... at this point I don't want to retcon this. What I need to know are the doppelgängers motivations. Does he care about the soul monger? Does he want to escape? Does he just want to murder everyone? If he needs to impersonate Moon for a long period of time... he will need to get Moon's stuff... especially the keys” Jeremy: “He wants to kill the party. Moon being his first, because of equipment.” Matt: “So... I have to figure out how to kill Moon without loosing his stuff.” Jeremy: “Yup. And Moon will be oriented to his new body. And realize that the new moon is not him.” Matt: “I mean... if I stick his bat head into a globe of destruction...”

I text Matt “You are now a bat.” Then I describe the scene: “Moon and Erd, you appear in a room of mirrors. Fluttering around is a bat. You wait but Pox does not appear.” As they consider what to do, I text Matt “You are a doppelgänger act like it.” Even before I’ve sent the text, Matt has stepped into the role of playing the new Moon.

Quickly, doppelgänger-Moon bags the bat. Then doppelgänger-Moon and Erd trek back to the rest of the party. We leave the session at that.

Matt and I exchange some texts, to clarify our understanding. And I proceed assuming that the party will figure it out. Polymorph lasts one hour, events will need to progress quickly before bat-Moon reverts.

At the start of the next session, the party calls for a long-rest. After some half-hearted discussion, the group sets the watches to:

  • doppelgänger-Moon and Octavion (an awakened lizard)
  • Erd and D’John (a Dao NPC)
  • Tlad (a drow NPC) and X
  • Regina and Lakuna (a human NPC)

I see Matt start to text me, and I realize I don’t have my phone. So I say “Oh crap, I must’ve left my phone at home. I need to text Jenny to reminder her to give our dog it’s medicine.” With that, we proceed with understood intentions. I’ve been playing with Matt for 31 years, we complement each other quite well, and can collaborate on something such as this with minimal communication. Throughout the remainder of the session, Matt drops very subtle hints: “I don’t have any goodberries, I used all my spells for the day.” Once curious, doppelgänger-Moon becomes quite cautious; Because doppelgänger-Moon does not have Moon’s preternatural senses nor perception.

With no strong preference for who takes first watch, I randomly roll. The first watch falls to doppelgänger-Moon and Octavion. I roll some dice to check for random encounters. No random encounters. Had I rolled any other pairing as first, the real Moon would have reverted.

I narrate an uneventful watch for all. But off-screen during its watch, doppelgänger-Moon did the following. First, he strangles Octavion. Then grabs the bag with bat-Moon and sneaks over to the sphere of annihilation and dips the bats head into the sphere. The body reverts, doppelgänger-Moon pillages the items, and tosses tabaxi-Moon and Octavion into the sphere. He then cuts/tears a hole in the bag.

A bit of time passes before they realize Octavion is gone. I played Octavion as extra chatty. Always talking to fill the air. With Octavion gone, I opted for silence. The party checks with doppelgänger-Moon, and he pulls out the now empty bag with a cut in it. The party, rather confused wonder about this talking lizard and it appears they think the lizard did something and fled. I’m sure their rattling around ideas.

Second Session

In our session, Matt has given an admirable performance. Matt established early in the campaign that Moon had an aversion to water: He would not get in the boot; and he would not step into shallow water. In the second session of infiltration, doppelgänger-Moon offered to explore a diving cage partially submerged in the water. He no longer offers to scout ahead. Some of this you could attribute to the influences of trickster gods, influencing most everyone.

Third Session

In our session, Matt again delivered. He continues to offer to go into the water. He avoids scouting. He keeps his distance. When the party faced a complicated puzzle room, he chose to separate from the group. When, during his separation, the Dao NPC companion died, he disposed of the body.

Fourth and Fifth Sessions

In our session and session, Matt continues to make excuses about not having goodberries; “I cast all of my spells for the day.”

Sixth Session

Matt missed our session, in which the party routed a coven of night hags.

Seventh Session

Knowing they were drawing to a close, in our , the party sought a long rest. But Withers, the tomb custodian, had plans to disrupt their rest and prevent them from gaining access to the Soulmonger.

Jeremy: “We'll both need to keep an ear out for when Alex casts True Seeing.” Matt: “Yeah... but more importantly... the amulet may provide me a way out without needing the party depending on how it works. I should note... Sleight of Hand is one of my four... now very reliable... expertise skills.”

The party defeated Withers and company. And Regina (played by Alex) found a potent object. Before they resumed their long rest, the Barbarian Wizard cast identify to understand the amulet; It would allow one person to teleport into and out of the tomb.

I told the players to level up their characters, because they would be getting an uninterrupted long rest.

Eigth Session

For our session, we started with a long rest and a cut scene. From an administrative stand-point, we had 40 minutes before dinner was ready. We spent that time narrating the cut scene and talking through the inevitable fallout.

Matt: “Does Alex sleep?” Jeremy: “Yes.” Matt: “I think I would try to take the amulet before the end of my watch an attune to it. Then sneak away. Leave the keys behind”

X (played by Paul) you wake a bit confused. Moon should have woken you up for your watch. You see a pile of keys where Moon’s bedroll should’ve been. Moon is gone.

Cut to an hour or so before. Moon waiting until all are asleep, quietly and delicately lifts the amulet off of Regina’s person. He then packs up his things, and leaves the five keys.

Without glancing back, and quiet like a wraith, he leaves the encampment and sneaks his way through the Tomb, up towards the entrance. He takes the amulet, attunes for an hour, and poof he disappears from the tomb, leaving behind all of his possessions.

From that point forward, the party cursed Twelvevine Moonshadow, the tabaxi ranger.


It has been a great run with a doppelgänger in the party, especially since the doppelgänger needed help from the party but had a goal of getting out of the tomb.

And it was fitting that the doppelgänger betrayed the group in the penultimate session.