Acheval Dreissen

An important figure in Snake Crest. In the middle of a fierce battle during the Arthur Tragedy he killed his mother. Possessed by madness, Ramius and Acheval's mother was the one who started the Arthur Tragedy, killing many Zero Knights who tried to destroy Snake Crest amidst the chaos. Distraught that Ramius might end up on the same path as their mother, he tried to push Ramius away from the path of a knight.

Unbeknownst to even himself, he is the Black Knight, but Millet uses her power to suppress his memory of this while he lives his normal life.