> born to the god of chaos and the entity of the void before the latter's betrayal and true colours were revealed
> was born twin to michael, ascendant of light, both lived with their mother before their sealed father managed to create a crack in dimensions and abduct them
> both suffered under this time, made to fight and become soldiers for their father's inevitable attempt to destroy reality (for the void, leviathan, hates what he cannot touch, can't have), michael was killed protecting lucifer from their father and lucifer was fatally horrifically scarred trying to escape to safer regions of the void with his dying brother.
> Michael fused his soul to lucifer's to save him, sometimes Lucifer can hear what sounds like michael speaking to him, his scarred eye lights up white with hairline fractures down the cheek and neck at these seemingly random times.
> that time he was literally enslaved to his will and made to fight and very nearly kill his younger siblings