Aaroniero
Arruruerie

Aaroniero Arruruerie is the Noveno Espada and the only one who is still a Gillian, which should make him the weakest thing in Las Noches. It does not, because his ability is absorption: eating a Hollow gives him its powers, its form and its memories, and he has eaten a great many. Two faces float in the tank where his head should be, and they finish each other's sentences.

He fights Rukia Kuchiki wearing Kaien Shiba's body and voice, because he consumed the Hollow that had fused with Kaien and inherited everything in it. He knows what she did, why she did it, and exactly how to describe it back to her. The whole fight is him asking her to accept that Kaien has been inside him the entire time and that killing him kills what is left.

Rukia beats him by using Kidō directly, which he admits afterwards was the one thing that could have hurt him. His aspect of death is greed, and it fits: he took a captain's Shikai, a dead man's face and a woman's worst memory and used all three at once. The tank breaks, and what spills out is not a person at all.