History (Aborted Timeline)
When the Duke of Soleanna and his researchers began attempting to harness the reality altering abilities of the god known as Solaris, he accidentally split it apart which resulted in the birth of two demonic entities: Iblis and Mephiles the Dark. While the feral Iblis became the embodiment of Solaris' fiery elemental powers, Mephiles gained Solaris' intellect and cosmic power.
When Mephiles attempted to flee from the laboratory that once held Solaris prisoner, he was stopped by Shadow the Hedgehog, who had traveled to the past in order to seal Mephiles away inside the Scepter of Darkness.
During his imprisonment, Mephiles formulated a cruel and brilliant plot that would span over two-hundred years. Years later, Mephiles was freed from the Scepter of Darkness and stole the form and abilities of Shadow (who at that point had not yet traveled back in time to imprison Mephiles in the Scepter) by merging with his foe's shadow.
He then traveled to an alternate future where Iblis scorched the world with the Flames of Destruction and manipulated Silver the Hedgehog and Blaze the Cat into believing that Sonic was responsible for their future and had them aid him in collecting the Chaos Emeralds.
Once he finally acquired all seven emeralds, Mephiles used their power to merge with Iblis and become Solaris once more. Mephiles was later erased from existence, Sonic and Princess Elise III aborted the current timeline by extinguishing the tiny white flame that was Solaris of the past.
An alternate version of Mephiles was captured and imprisoned in the Zone Jail by the Zone Cops for presumably the same crimes his counterpart had committed. Unlike his more sadistic, dramatic and uptight counterpart, this Mephiles was more laid back like Sonic the Hedgehog and had incorporated words such as "Dude" into his vocabulary.
He was seen hanging out with a fellow universe-annihilating prisoner named Void in the food court when the Destructix saved an ungrateful Scourge the Hedgehog from a group of prisoners and asked Void what Scourge's problem was though he was never given an answer.
Later, during a massive prison break, Mephiles was seen sliding down a pole as he made his escape alongside other prisoners like the ultra-powerful Robolactus and an evil version of Cream the Rabbit, but was presumably recaptured when Zobotnik brought in as many reinforcements as he could and has since continued his daily routine.