The Origins of Evil
Given Mephisto's nature as a devilish liar, the true nature of his early days remains shrouded in mystery. According to one telling, in the wake of Atum, AKA Demogorge's attack on the planet's demons billions of years ago, humanity unintentionally forms a new line of demons and devils through their dark desires. Thus was born Mephisto, a demon and Lord of the Splinter Realms, one of many devils ruling over their own fiery realms.
Another telling starts four billion years ago, when Mephisto appeared on Earth as a maggot-laying fly as the diseased Celestial bleeds its fate-changing blood into the nascent planet. From there, he begins manipulating creatures all over space and time, causing trouble for the prominent orb. He can also return from death almost immediately, in most cases, thanks to humanity's penchant for evil. Still, given his place in the cosmos, Mephisto seems to be held to a certain set of unknown rules that prevent him from simply taking control of reality for himself.
