Latest appearance: Fighters of Lapis 4
According to Sonic 06, he (along with his counterpart Iblis) was created after a failed experiment known as the Solaris Project, which was a plan for humans to be able to travel to the past or future. Mephiles was sealed into the Scepter of Darkness for ten years, until it was shattered by Shadow the Hedgehog. However, with Sonic the Hedgehog and Princess Elise having blown out a candle and reversed the events that happened in the game, Mephiles's true origins are unknown.
Mephiles is much more sadistic than most Sonic villains; he enjoys the harm and distress of others, as well as the destruction of everything. He is also known to be a master manipulator, using the future as his basis. An example would be telling Shadow that the entire world would betray him, including E-123 Omega.
Mephiles, being the lord of darkness, can use it to create small, flying creatures that assist him in combat. With a Chaos Emerald, he can travel through time, create an army of (usually irregular) clones. He can also use the Dark Chaos Spear, which he used to murder Sonic in the final story of Sonic 06.
Silver Spurs Saga
Mephiles appears in The Crossover Vacation as the main antagonist. He desires to destroy the Spursverse (known in the series as the meta-universe) by harnessing the black hole-esque gravitational pull of the Void.
It is rumored that he will return in Echoes of Disaster, the final addition of the series.
In Fighters of Lapis 4, Mephiles appears as an unlockable character.