One Night Ultimate Werewolf is a fast social deduction game in which every player has a unique role with special abilities. Unlike classic Mafia, the whole game takes a single "night" and one round of discussion.
At the start everyone receives a role: there are werewolves, villagers and characters with special abilities (a seer, a robber or a troublemaker, for example). During the night players take turns performing their role actions (often with their eyes closed), swapping or learning roles.
During the day everyone discusses what happened and tries to work out who the werewolf is. At the end a vote takes place and the chosen player reveals their role.
Victory depends on the roles: the villagers win if they find at least one werewolf, while the werewolves win if they manage to stay undiscovered.