Nebula

"Mine! My Master! You lot can go die in a corner for all I care! But she...she is mine, and mine alone. Do not come near her."

- Nebula monopolizing her Master. Nebula (ネブラ, Nebura lit. Cloud) is a Celestial Spirit who was banished from the Celestial Spirit World, due to her monopolizing her previous Master for herself, which costs the life of her Master. She was later confronted and modified by Azazel and converted into a Maken, becoming a "black key", and Maken #5 (魔剣ンバー五, Demonic Sword Number Five), representing Greed, and then dubbed Mammon (マモン, Mamon lit. Greed) by Azazel, as her Maken name.

Trivia

 * Nebula's appearance is based off of Kuro from Fate Kaleid Prisma Liner Ilya.
 * Nebula refers to an insterstellar cloud that exists in space, and are often star forming regions.