Ankou (nicknamed often as Anki-Doku) is the "entity of Death" in the French Folkore and made several appearance in the Oasis Dimension. As one of Death's servants, he wanders the vast universes and give the punishment to those who are damned. His powers are beyond from any powerful beings, Ankou's feats have no limits when it's about to growing. Ankou was here since many hundred of years due to his powers, even said to be close to the Gods. He want also to discover who he is.
Ankou also appears in Anatawa series, such as Anatawa and Anatawa 2.