Abbot of Unreason is based on a tradition in the British Isles where a commoner was appointed by lot to preside over the Feast of Fools. There are several different versions of the festival and position arrayed over time and geography. The plan is that this person serves as the de facto king during the feast and his (or her for game purposes) commands are obeyed by all present.
As a game, Abbot of Unreason is intended for 4-6 players, each of them hoping to become the Abbot of Unreason. Of course, determining by lot wouldn’t make for much of a game, so instead the game is played in rounds, with each player taking a turn as the Fool Pro Tem and the other players participating in a challenge posed by that player.
At the end of several rounds (typically 2 per player), the player who has won the most challenges is deemed the Abbot of Unreason. All players can then narrate the Feast of Fools if desired. If there is a tied at the end of the normal rounds, a tie-breaker is chosen by the remaining players and the winner of that tie-breaker is the Abbot of Unreason.