Millenia is from a savage demon world where civilization has never had a chance to survive. Powerful demons roam the world, battling each other in a near-constant war. Millenia may be the most powerful of them all. Upon being summoned, she quickly attacks her summoner. She is subdued entirely by accident and bound to a contract that forbids her from harming others while summoned. She is highly ambitious and resents being bound to a contract. She follows every order she is given, oozing with hatred and disgust. She despises her summonner's lack of ambition and promises she would conquer the Earth for him if only she were unchained. Her summoner has no interest in world conquest, prefering instead to use her for sex. After years of being summoned she resigns herself to her fate and seems to mellow out. She enjoys watching movies and learns a lot about Earth culture. She gives birth to many half-breeds on her world, and when one of them is injured by a rival the pain in her heart is so severe that she resolves never to allow it to happen again. She curses her summoner for inflicting human weaknesses upon her, and sets out to crush all of her enemies and build a peaceful civilization where no harm can come to her children ever gain.