Cassiopeia

Cassiopeia "the Seated Queen" is a powerful Celestial Spirit that sold her normal form about decades ago for more power, but she is also considered the most beautiful thing in the world for the aura that she emmits from the stones. It's actually Mirio's power house, and only uses her at extremelly rare situations.

Personality
She doesn't speak or have a face, but legends told about a vain woman that can be summoned. Her face was the key for one's destruction by distracting the enemy at a battle, no matter the gender. With a extreme pride and avarice, Cassiopeia wants all the power of the stars, and to control the Celestial Word and became the Supreme Queen, but the only thing she had to do is to abdicat her body and seduction for magic.

Tears can be seen at the women "eyes" at every side of the stone, the only vestige of the humanity that the Queen will never had.

Magic and Abilities
Soon.

Immortality: As a Celestial Spirit, Sagittarius cannot die, unless he is somehow forced to stay in the Human World for too long without returning to the Celestial Spirit World once; something which would slowly deplete his life force, eventually resulting in his death.

Trivia
Cassiopeia is based at Alilat, of Shin Megami series.