This creature only attacks the player who turned the chapter card - even if the other players are attacking it (which they definitely should take the opportunity to do, unless of course one of them wishes to REST).

When a survivor becomes Marked for death (found in adventure pack 1), if their cult die gets added to the row of chapter dice, they will be out of combat. In this case (and other similar cases), the creature will change its target to the survivor with the most health. In the case of a tie, the creature will attack all tied players.