After Uriel gracefully stomped out of Heaven to wage war against God, a game of 5D chess began between the four major archangels, as well as Lucifer. A poor, unfortunate, mortal soul known as an Avatar is divinely linked to each of the archangels, destined to be an aid to their angel in some way across all realities. While generally, the angels themselves are mentally separate entities between realities, their avatars each share a single conscience across all of their splintered versions (i.e., every reality that Lanzia exists in, she shares the same conscience). For this reason, they're sometimes called Multireality Conscience Singularities. It is an avatar's job to inform the various splinters of their angel about goings-on between realities, in order to be able to gain an upper-hand.

A note about Lucifer:

His avatars work differently from the rest. Lucifer does not have a multireality conscience singularity. Instead, he can make soul-binding contracts with mortals. Every mortal bound to a contract in one reality splits Lucifer's power evenly. The more pacts Lucifer has, the less potent the contract is. If he has made a pact with someone in a different reality, he will be able to see their other lives through their eyes, and will then know that he has encountered them before.