Board Thread:Lore Discussion/@comment-72.77.73.35-20140408131341/@comment-16047389-20140408210432

Nocturnal would claim the Dragonborn's soul, as the choice to become a Nightingale is the act of willingly and knowingly swearing allegiance to her. Becoming a werewolf could be completely accidental or done while unaware of Hircine's claim on werewolves. Of all the Daedric Princes, Nocturnal is the one with the most rightful claim to the Dragonborn's soul. The others merely declare him/her their Champion, while the Dragonborn actually swears service to Nocturnal.