The Ash Ghoul Sybille can smell Auras.
Edit: Apparently she uses Venthyr Death Magic not Void to heal herself from the Light… No idea why the Spell use the term “whispers in your mind” though… In any case she seems to be the only Venthyr who recognizes the Nathrezim by scent which would suggest that a Venthyr would need to know what an Immortal Demon Hunter is to recognize them by scent.