This is for a mafia:
Basically, there are two teams of players, civilian and mafia. The civilians are told there are mafia players wanting to kill them. Everybody poses as a civilian and only the mafia know who other mafia are. During the day, all of the players discuss things and vote on someone to lynch in hopes of killing the mafia. They can vote to lynch someone or vote a no lynch. Whether they kill a civilian or a mafia isn't known until the lynch is committed. At night, the mafia is able to kill one person of their choosing. Let me set up an example.
There are 8 civilians and 4 mafia.
Day 1: Players vote no lynch.
Night 1: Mafia 1 kills civilian 4.
There are 7 civilians and 4 mafia.
Day 2: Players vote to lynch Civilian 2. (Thinking he is mafia.)
Night 2: Mafia 3 kills civilian 7
There are 5 civilians and 4 mafia.
Day 3: Players vote to lynch mafia 3. (Thinking he is mafia.)
Night 3: Mafia 1 kills civilian 1.
There are 4 civilians and 3 mafia.
Day 4: Players vote to lynch mafia 2. (Thinking he is mafia.)
Night 4: Mafia 1 kills civilian 8.
There are 3 civilians and 2 mafia.
Day 5: Players vote to lynch civilian 5. (Thinking he is mafia.)
At this point, the mafia wins no matter what since they outnumber the civilians. Even if the mafia expose themselves, the civilians can't vote to lynch the mafia since the mafia overrules them. The mafia can then kill them all one by one until the civilians are dead.
Result: Mafia wins on Day 5.
This is only a model for a simplistic version of the game. You should feel free to throw in some twists of your own kind for your game.