- You may be looking for the Shadow Devil.
Dr. Eggman and Dr. Wily, seeking to create another line of defense for their Wily Egg battle station, came upon another idea combining concepts from both their universes. Capturing Chaos, they merged it with a Devil Core to create the Chaos Devil. It was later accidentally released by Rouge the Bat during her mission to bring down the Wily Egg from the inside. The monster was swiftly kept tame by Metal Sonic and Bass but not before it was able to trap Rouge inside its body. Once the monster was moved back into it's containment tank, the captured Rouge was taken to be roboticized. Despite the upset, the doctors took the encounter as an indication that the Chaos Devil was fully functional. It later appeared again to engage Sonic and Mega Man as they made their way deeper into the Wily Egg, but was engaged by the heroic robot Duo. After a heated battle, Duo freed Chaos from the Devil Core and destroyed it, and the pair were then caught up in the effects of the Super Genesis Wave. (MM: #27, SU: 53, StH: #251)
The Chaos Devil possessed many of the abilities of Chaos and the Yellow Devil, and was capable of shifting its watery form in various ways. These included forming limbs or even additional mouths on its form, and protecting its Devil Core eye from attacks.