OK the idea that I want to expose you is very simple, that is a boss rush. Something similar to the Bloody Palace of Devil May Cry to be clear or Mushin's tower in Blade and Soul.
We have a dungeon (our Bloody Palace) divided on several floors, and on each floor we face a boss. Defeated the boss "accesses" the next floor and so on.
You exit the dungeon when you are no longer able to continue, because you can not defeat the boss, or defeat all the bosses, thus completing the Bloody Palace.
it's a rough idea, but I think it's possible to make it happen. What do you think about?