Shortest version possible:
My Homebrew is a multiverse that connects a few different campaigns together and allows cross over between different play groups.

Each universe has its own set of deities based on the campaign and lore. The only true deities are unknown to most of the multiverse, they are called "Hero" and "Villainy" they represent the two parts of my mind as the DM that want to tell heroic stories and challenge the players.

A group of Mystic Nomads police the multiverse keeping things in check between realities.

One time I handed the reigns of DM to someone else and I made a character, that DM didn't work out and I took over again, turning my NPC into the BBEG. This is how "Villainy" incarnate entered the world as a Mystic Telepath Orc known as "Vile".

Over a multitude of campaigns Voldemort style, Vile arose to become a major threat to the multiverse.

I recently moved to a different state and as a farewell we had one final session comprised of all the players' favorite characters brought together throughout space and time to finally kill Vile.

But in doing so they killed 1/2 of the true godhead and the multiverse collapsed...

My new world was born out of this. Vile had a son, that child exists suspended in the Aether void being tended to by his Uncle Hero. My current campaign takes place in the dream of Vile's son. When we awakens that world will be destroyed and together Hero and Vile's son will build the new world, inspired by the dreams he had.