Crewmates need to stick together and gather enough information about each other to determine who the Imposters are, then convince their allies to "eliminate" them.
Imposter The Imposters look exactly like Crewmates, only evil. The Imposters have three ways of winning: Killing enough Crewmates to have the majority, booting them out the airlock or managing to destroy the Reactor or Oxygen supply.
The Imposters have to blend in with the Crewmates, taking them out and lying their way through the emergency meetings.