It seems to me that Iris, with her griffons, will defeat anyone in a duel.
Iris's counter-hero is Deirdre; she usually wins. Ossir, Leto, Orson, Nimue, Carli, and Ibba have decent chances (50/50, or slightly less). In principle, with good luck and not-so-perfect play from the opponent, you can defeat her with almost anyone. Except for Deiro and Daleb, it's very difficult.
