In the multiverse, the gods and all the other beings who rule have gone frustrated and annoyed at all the bad souls who always vandalises and destroys what they have built. After many years of discussion they decided to just throw them out of sight, where they can't annoy them any longer.
The place these poor souls are sent to, is a universe ruled by a dungeon. A dungeon given the purpose of keeping an eye on, and distracting these unruly beings. Like rats, they can't escape the dungeon, their only salvation from full insanity being the dungeons challenges, made for its own enjoyment.
The mc will be the dungeon as it creates planets and challenges for its inhabitants. This is a bit inspired from the novel "Earth's first dungeon" here on rrl, as i liked how there were a lot of different instances/dimensions with different themes and a lot of paths for adventurers to explore. A bit like the concept of putting worlds inside worlds.