Diem

Diem is the creator of the Multiverse, and the single most powerful being in it. The Multiverse exists because he willed it. Essentially, "Diem thinks, therefore everything is."

Origin
No one is completely certain where Diem originated or anything about his history before the creation of the Multiverse. However, it is rumored that he came from a vast ur-universe known only as "Earth".

History
After the first moments of the Multiverse's inception, Diem began the process of creation. However, his thoughts and competing desires were chaotic and unfocused, and all of his creations were horrific non-Euclidean aberrations. These monstrosities disgusted him, so he trapped them all in a self-contained bubble of the Multiverse. Thus he had created the first universe, and named it X'dalzot, and sealed it shut with a Living Gate so that they would never touch the rest of the multiverse again.

Realizing that he could not trust the task of creation to himself personally, he created two beings as two separate aspects of himself. One apect took the form of a God, and the other took the form of a Goddess. These two aspects would balance each other, like yin and yang forces, and thus would be able to build stable creations. He set them on the mission of creating universes to populate the Multiverse in his name.

Since then, he's basically just sat around like a lazy bum.