Grease

Alleged criminal put through the wringer and gone over the deep end. Hunts other Masked with an improvised nailbat and a superspeed ability that grants him apparent teleportation.

Originally captured and memory-locked for "knowing too much," Grease sacrificed himself in a prison break to be corrupted into a Masked (he was supposed to be rescued, but the timing went awry). He roams as a feral beast for a while until his former prison friends, Golden Midas and Viis, catch him and attempt to rehabilitate him.

Eventually Grease decides he doesn't really belong with their misfit band of vigilantes and breaks off to go do his own thing as a more sentient Masked.

His soul is contained in his mask and he 'malfunctions' when separated from it.