u/Darkhog

So basically have a structure generate in the world that is a tower of infinite height. Each floor will have more and more dangerous monsters (multiple boss-level monsters on higher floors), but also more and more valuable loot. Monsters would respawn (but not while player is nearby), but the loot wouldn't.

So the player would be forced to go higher and higher in order to get better loot from The Tower and the return trip would usually be done with a glider/parachute out of a balcony (on each floor of The Tower).