サマエル

A fallen angel who commands venom and death, Samael is the very incarnation of the immortal, unaging serpent. She is suspected as one of the culprits behind the Divine Calamity.

Her charming looks are paired with a cruel personality - she wields her Death Scythe with little regard for mercy, slaying all those who dare oppose her. Her particulars are vague, ah, so vague. Vague beyond measure. In fact, she might have been misjudged all along, having done nothing of particular gravity. Ah, but let us not dwell on trivialities. Simply put, her smile never fades; her days are colored with joy and fulfillment. Nary a problem to be found in there, really.

From the very day they met, she's taken a liking to Tendou Setsuna - she could tease and torment him for days on end without ever tiring.

MangaGamer