As heroes complete quests, they will have to fight a boss. Tackling a boss takes the same time as the regular quest, but requires 25% more power. Each time the boss is beaten, the quest power increases by 10%, the drop rate increases, and the number of steps before encountering the boss again increases as well. Beating a boss awards more resources than regular dungeon runs. But if you fight the boss too many times, your adventurers won't be high enough power to continue to run the quest.