Need help with a Doppelganger campaign

Christopher McArthur · Jun 18, 2018

So as the title implies I am currently in need of help constructing a particular campaign. I am a pretty new DM. I'm struggling with a concept of an investigation / psychological thriller style campaign based around the idea that a town is slowly overrun by Doppelgangers and Mimics being controlled by some kind of hive mind queen or something. I'm having difficulties coming up with things for the party to do / investigate / fight. Any help would be greatly appreciated.

There will be 4 players starting off at level 3. The campaign needs to be about 10-12 sessions long.

Here's what I have so far:

-Doppelgangers replace people 1-2 a day. There's 1 mimic for every 3 Doppelgangers. The mimics don't do anything until commanded.
-Have a wizard in town that helps provide clues. She eventually ends up being replaced by a Doppelganger.
-Their first clue comes when the Wizard tells the party about Orcs being seen in a nearby swamp and around town. When they go to investigate, the Orcs are actually Doppelgangers as well and some people are tied up in a camp or dungeon.

Eltab · Jun 18, 2018

Have some of the 'standard enemies' first, and bring in the Dopplegangers as the 'string-pullers behind the scenes' sort of mastermind.

Orcs arrive in the area and must be defeated before they pillage everything valuable.
Local Wizard goes to check out Orc encampment after PCs defeat them and celebrate victory; he comes back with worry wrinkles all over his face
He found a single doppleganger in the Orc Chief's private tent; he doesn't know if it was imitating the chief or an advisor
The local crime gang targets the PCs; they eventually discover the crime boss is actually a doppleganger.
Several dopplegangers 'gang up on' the PCs, bringing reinforcements along with
Head doppleganger is discovered (by the local Wizard?) and can be targeted for assassination
How do dopplegangers breed? Destroy the "nesting area" and solve the problem for permanent

You will need to establish how many dopplegangers are in the area to start with, so this is not an endless treadmill.

aco175 · Jun 18, 2018

One doppelganger can be enough in certain circumstances. By impersonating the local orc chief he can start an uprising with local tribes and eventually set raids upon the local town and villages. The orcs only know that their leader is acting different than normal and are most likely fine with attacking the villages and doing what orcs do. The PCs meanwhile are dealing with orcs and their uprising as to why it could be and stumble on clues pointing to a doppelganger. Once he finds out that the PCs are on to him, he could now take over the local lord and frame the PCs, or look like a PC and kill the mayor in front of the town trying to get the PCs arrested or thrown out of town. A lot of carnage can be made once everyone is angry with everyone else and think that they live with a bunch of murderers.

Maybe the regional lord sends a sheriff or paladin type to bring order the the town and starts to clean out the place only to be captured by the doppelganger. This leads the PCs to investigate and free him and eventually save the town in a move showdown where the actual lord and imposer are trying to get the town or PCs to kill the other.

A town full of them can even be worse. A great twist is to have 2 groups of doppelgangers working at odds with the others and maybe not even know that the other group is in town. Now you have the 2 ganger groups and the PCs working different angles and perhaps even work with one group to take out the other before realizing that they need to take out the other group next.

Christopher McArthur · Jun 18, 2018

I really like the different Doppelganger groups kind of butting heads and using Orcs to do their bidding. No idea how I missed the classic showdown of a Doppelganger and a real person. Thanks for the awesome suggestions!

Christopher McArthur · Jun 18, 2018

I like the idea of the Doppelgangers targeting the party. It's something I didn't think of that would be an awesome way to put pressure on the party. Thanks for the ideas!

Paul Farquhar · Jun 18, 2018

At least one of the PCs needs to turn out to be a doppleganger. Give them amnesia, then they can't be sure if they are not all dopplegangers.

Christopher McArthur · Jun 18, 2018

Oh my god yes! This would add to the paranoia SO much, thank you!

jgsugden · Jun 18, 2018

Invasion of the Body Snatchers. It might work best as a shorter story... when there is a 'secret' focused campaign, it can come to a head faster when the secret gets out. To make it work over a longer period, you need to isolate the Doppelgangers to keep their nature suspected, but unproven.

I had a Doppelganger (technically half dragon doppelganger) as a major BBEG in my campaign world for about a decade. What allowed me to run that longer was:

1.) The PCs heard about the NPC for *years* before they met him (outside of a brief encounter with him when they were first level that set the stage for a long term storyline).
2.) When they met him, he made sure to control the situation. He wanted them to perform a task, but rather than go to him and ask, he set up a situation where they were looking to him for information. Despite a reputation as a crime lord, he gave them the information freely. When they next came to him he was chastising some of his underlings for failing to complete the mission he wanted the PCs to do... and they volunteered to do it for him without him ever asking. As a DM, I intentionally did the subsequent encounter on the fly to support the optics that this wasn't something the Doppelganger planned to have them do. From there forward, they met with his minions more often than him, and when they met him he made sure he had complete control ... often encountering them when they were depleted of magic.
3.) He had other Shapechangers in his service, but they were not the majority of his troops. They were rarely the leaders in their community, either. Instead, they were key advisors, or beings close to key advisors. They indirectly influenced the world. Most of the NPCs on his payroll had no idea of his true nature or goals.
4.) He had contingency plans for when his nature was discovered. The PCs believed that - rather tan be a Doppelganger the entire time - he'd been replaced by a Doppelganger at some point. They actually 'rescued' him at one point. When it was undeniable that his true nature was being discovered, he faked his death and slipped into another role that had been set up (and he'd played on rare occasion) for years as well.
5.) His long term goal was to travel back in time before a different Big Bad existed so that it would stop hunting him. While being a criminal mastermind offered some benefits that he enjoyed, it really made it easy to run him when he had one major objective that took a huge number of steps to achieve.