Seilah

Seilah (セイラ Seira) is an Etherious of the Dark Guild Tartaros and its team: the Nine Demon Gates. She is a major antagonist in Fairy Tail.

Seilah is a calm, collected woman who has a habit of making allusions to the structure of books in her speech, however, like all the other true Demons of Tartaros, she is incredibly cold and calculating, as well as extremely merciless as demonstrated when she unhesitatingly forced Elfman Strauss to attack his sister Lisanna, and then proceeded to use her as a hostage so that he destroys the Fairy Tail Guild on Tartaros' behalf, even smirking and blushing upon seeing the apparent realization of her plans completed with the guild buildings explosive destruction. She is also extremely loyal to, and bordering on infatuated with, Kyôka, referring to her with the honorific suffix "-sama," and engaging in implied sexual behaviors with her.

Her admiration and devotion to Kyôka goes very far, as after realizing that her plan to destroy Fairy Tail ended up putting Tartaros at a disadvantage and her being made a fool of in front of her,[she angrily sought vengeance against Mirajane, as she was Elfman's sister. Lastly, her loyalty does not rest solely upon Kyôka, she is also very loyal to Tartaros and the innate desire of the Etherious race (to kill Zeref), and thus endangered her own life by giving Kyôka the remainder of her Curse Power so that she, as the last member of the Nine Demon Gates, could achieve Tartaros' goal of "returning to their creator."