Athos is an archsage, an especially skilled and experienced sage, who appears later on in the storyline of Fire Emblem. He becomes playable in the game's final chapter. His skill and power, however, are practically unmatched and he joins the group equipped with a series of especially powerful spells.
Athos is one of the eight legendary heroes of the "Scouring" and is considered only a myth by those who have not met him. He rarely takes apprentices. However, at the time of the events in Fire Emblem, Pent is his sole trainee. In the final chapter of the game, Athos confronts Nergal single handedly, however, he only manages to wound him.