Satella

Satella (サテラ) is the Witch of Envy.

Appearance
Satella has a thin body with long silver hair and purple blue eyes. When Subaru encountered her at Echidna' tea party, she wore a black dress made of shadows that seemed to wave in accordance with her heartbeat. Initially, Subaru was unable to see her face because of a black shadow covering her above her neck, which was created out of his reluctance to accept her, however he later accepts her and becomes able to see her face, later mentioning that she looked exactly the same as Emilia.

Personality
Contrary to popular belief, Satella and the Witch of Envy are separate personalities, formed when she took in incompatible Witch Genes. The two personalities tend to fight each other. Both personalities love Subaru, though the Witch of Envy personality is much more aggressive about it, while Satella is much more reasonable and cares about his well being.

History
400 years earlier, Satella absorbed Envy Witch Genes she had no compatability with, resulting in the creation of her Witch of Envy personality, subsequently going out of control and killing six other Witches of Sin while nearly destroying the world. Despite the efforts of many, including the dragon, the Sword Saint, and sage, Satella was unable to be killed, instead sealed in a shrine that is watched over.

According to the other witches, Satella is the one that swallowed the other six witches and half the world, and not the Witch of Envy.