I made a look before, but I got some ideas by thinking about him more as a dark energy he actually is. Because Mephiles is not a shadow look a like, he just took his form to have a body. So over all he is still a black mess of energy and darkness. So with my design I have, he doesn't look like shadow and I gave him some more explanation of what he is in my story. also thank you to
So here you go his story: After being freed from the Zone Cop prison due to scourge's Prison riot Mephlies made his way back to the future due to Killers help, through much of there adventure together they parted ways for the moment, Killer having returned to Kathy, mean while mephiles fought his battle against Silver, but over time mephlies knew he needed more power and more help to achieve his goal. Years began to pass and no opportunity began to show itself, becoming frustrated and angry his was less subtle and more direct. Upon stealing a ancient book from the echidna ruins "The book of Chaos" studying its works mephlies learned to use chaos energy the energy gave him power, but it did not save his dying presence. Forging Armor used by pure chaos he was able to keep his body together, he kept himself together, but that did not keep his mind sane, being a creature of darkness nearing an end, it drove him crazy.
Creating a smile to show others what darkness feels everyday to strike fear into others while in turn hiding his own fear. Upon one day Killer turned seeing how he had changed she was pleased to him so expressive with his new self, sharing her energy she preserved his form keeping him from fading, perhaps a band aid for the inevitable but mephlies did not care feeling killers darkness gave him such joy he felt complete once more. Thus losing his sanity slowly he makes the most with killer to sink the world in the darkness he wishes , " as All things must come to an end"