Deimos is the tritagonist of the Madness Combat series who first appeared alongside Sanford in Madness Depredation. He has a bandaged head, wears a headset and visor and has been seen wearing a vest with a white tank-top underneath. His first chronological appearance in the series is in Madness Combat 5: Depredation. He appeared again in Madness Combat 5.5 as one of the protagonists. Deimos makes his last appearance alive so far in DedmosRebuilt.fla, the final part of the canonical spin-off series, Dedmos Adventure. There's also a Greek god of terror under the same name, and the name of one of the two moons of the planet Mars.

More info can be found for the Madness Combat Deimos here.
More info can be found for the Greek god Deimos here.
More info can be found for one of the moons of Mars here.