Gamon was one of Hellboy's elder brothers, the son of the demon Azzael, and nephew of Astaroth. He and his brother Lusk were tricked by Astaroth into fighting Hellboy for the Right Hand of Doom.
Gamon attempted to take the Right Hand of Doom from Hellboy, attacking and wounding him. Later, when he insulted his father in the presence of Astaroth, his uncle decapitated him. Despite the decapitation, Gamon's head was still able to speak.
Gamon, Lusk, and Astaroth were eaten by Leviathan and are presumed dead.