The Colonel is a supporting character in Shadows of the Damned, a demon hunter, just like Garcia Hotspur, the game's protagonist. As his title implies, he is a former military man who ventures into the City of the Damned very heavily armed indeed. The first indication that there is another demon hunter in Hell comes when Garcia discovers a graveyard full of butchered demons in the shape of an X.
Next to nothing is known about the Colonel's background, as he refused to work with Garcia or even tell him his name, but a newspaper clipping inside the house where he was regrouping, plus some dialogue he shouts later, paints a bit of a picture: the Colonel's beloved wife, Maria Dominico, was horrifically murdered by one of the demon lord Fleming's Lieutenants, Stinky Crow, who completely flayed her body and made off with her skin. The Colonel then made his way to the City of the Damned hoping to bring Maria back alive, but he apparently recognized the chunks of meat hanging from Crow's clothing as being from Maria's body, and decided to slay Crow to avenge his love's death. Unfortunately, blinded by grief and rage, the Colonel was unable to defeat Crow, and when Garcia made it to the demon's lair, the Crow's Nest, he found the Colonel ripped to pieces and dumped in a pile. Despite having previously praised the man's skills at demon slaying, after his death Garcia coldly disregarded him, saying that he would have killed Crow if he'd had more skill. Much later on, though, Garcia admits that he wished the man hadn't died, if for no other reason than fighting his way through Fleming's demon hordes would be easier with another demon hunter on his side. Garcia's partner Johnson then muses that since the Colonel was killed in the City of the Damned, he is now damned to the Underworld and will probably become a demon, briefly wondering what he'd look like as a door-locking Cherub, the most juvenile form of demon.
Unlike Garcia, who wears no armour and relies entirely on his shapeshifting demonic companion Johnson for his arsenal, the Colonel used much more Earthly means to kill demons, wearing heavy tactical armour and carrying grenades, ammo clips, and utilizing a heavy machine gun as his primary weapon (although it is idiotically rendered in the exact shape of a grenade launcher). Like fellow demon hunter Garcia Hotspur, the Colonel has more than one facial scar, with his crossing over the bridge of his nose and forming an X, a nod to indicate that the demons slaughtered in the graveyard were indeed his doing. Interestingly, although the majority of real laser sights are red in colour, the sight on the Colonel's machine gun is white, likely to distinguish it from Garcia's own sights, which are colour coded red for revolvers, green for shotguns, and blue for machine guns.