Nightgaunt (Eddie McKinnon) is a member of the Children of the Night, working for the Necromancer. He's a cheap shot artist extraordinare. He carries lots of weapons and wears "a helmet that was featureless except for two devilish looking horns, a Batman-style cape and some obvious body armor," and he doesn't take the helmet off much, so much so that Vamp has never seen his face. He can travel through shadows instantly, and hide in them, a power taken with the costume from the previous Nightgaunt, a hero who this one killed. During the Boston Brawls, he shot Lancer point-blank, and later stuck a bomb to him, after which Bladedancer chased him through the shadows, though he escaped.
According to Diane Castle in a Forum message lost in the crash, Nightgaunt's "powers" come from a pair of power gems on his belt. We see them in Ayla and the Birthday Brawl: Chapter 12 - The Legend of Talus, or of Fortitude where Vamp is badgering him.