Aliens are a faction with a 1-shot factional kill. Typically associated with Great Idea Mafia variants, Aliens are an alternate groupscum faction. To offset the reduced power, Aliens win ties in endgame. Aliens typically have powerful roles such as a Prober (Combined Seer Roleblocker) and a Vanillaizer.
Aliens are a faction with a single factional nightkill. Aliens constitute an informed minority, they are small in number but have additional information. Similar to the Mafia, the Aliens know each other and may communicate privately with each other.
Aliens also win ties in endgames, in any circumstance the game would end with the Aliens in a tie, the Aliens are instead declared the winner.
Aliens may have access to more than one nightkill in larger games, or have access to an additional 1-shot factional ability.