At its core, Avalon is a game of social deduction and imbalanced information. It requires coordination, communication, and voting to expose the betrayal and loyalties of the players. It’s very similar to Midnight Werewolf, but there are additional roles and more bad guys depending on the number of players present.
The mechanics of this game include specialized roles, hidden role players (to their own and/or to other teams), democracy-based voting, clockwise team proposal, imbalanced information for users, and lots and lots of discussion. This allows people to stage a persona and convince others of their loyalty in the game. Each specialized character has its own quirks. You can also pick and choose which characters to include to make the game different every time. Hidden players would have to adapt quickly and find their team or convince their team of their status, giving them an additional mission from everyone else. And finally, the proposal of teams goes clockwise while the voting is majority-rule, which gives everyone a chance to participate, which helps make the game more balanced (especially as it gets hectic).
These mechanics and dynamics give rise to quite a few types of fun. Fantasy, narration (there’s a designated narrator and the storyline progresses depending on characters’ choices), and fellowship/competition (each team is trying to collaborate and win without being found out). The subcategories can also include challenge and expression, as players may use these personas to express a new version of themselves without devoting to that personality (deceiving friends and sabotaging missions). Personally, I really like the discussions that come from these and the shocked faces of friends when they find out the truth. I’m also a big fan of everyone getting to propose a team and state their reasoning, which allows quieter friends to have fun too.