Don't known if tendrils of darkness is a bug. Theres another peril maybe correlative to the next campaign that make you lose the quest in fewer turns.
I think it's too much. I don't want to be babied either, but c'mon. When the app tells you to apply 18+ damage to all heroes in a game where the highest base Health is 14 (unless I forgot somebody) that's just boring and feels cheap. Besides, in this game, taking 2 or 4 damage per round is a huge game changer already. Lemme go out in a blaze of glory during combat instead.