As the game goes on, you will begin to empty stacks. At the start of any round after at least one stack has been emptied of all conflict cards, you may decide to face the boss in the endgame. If all three stacks are empty, you must start the endgame.

Ignore empty stacks for all game effects. Cards cannot be returned to a stack once empty; if one would be, discard the card instead. If more enemies would be activated than remain in the stacks (due to ), activate as many as possible and ignore the rest.