As Captain Britain, Brian was empowered by the legendary magician Merlyn and his daughter Roma and assigned to be the champion of the British Isles and its peoples, as well as the defender of Earth-616 as a member of the multiversal Captain Britain Corps. Following his corruption by Morgan le Fay, his twin sister Betsy reclaimed the mantle of Captain Britain, with Brian taking up the moniker Captain Avalon as defender of Avalon.