Man-At-Arms is Duncan, the chief weaponer of Castle Greyskull. He fights a never-ending battle to protect Eternia from Skeletor and from Skeletor's evil armies. He is a briliant scientist, able to create impressive machines and gadgets. He is an expert at fighting with plasma guns and rocket launchers. He is one of the few beings in Eternia who know that He-Man is Prince Adam. He is Teela's father.