Coup: Reformation
Worth itBGG rates it 7.25 from 6,153 ratings. It is the main expansion; a BGG thread calls base Coup plus Reformation the complete game, and it extends play from 6 to 10 players.
Needs: Just the base game
Adds: 15 additional character cards and faction rules: each player is Loyalist or Reformist, can target only the other faction, and can convert by paying the Almshouse.
Fixes: Lets Coup play well with up to 10 players and adds early tension for four or more.