Glaukos

Glaukos is reputed to have been the first ruler of the city of Eidyla. He disappeared after apparently being defrauded by Sisyphus, who replaced him as ruler, and after he ate Diktamnon herbs, that reputedly turned him into an immortal fish.
This reputation turned out to be true, as Pyro, who had been changed into a fish, was led to him by his ichthyan servants. Glaukos told Pyro that he had been overthrown by Sisyphus, and that he had turned into a fish-like man while he bides his time. He claimed that Sisyphus had managed to capture Thanatos, which ended death for as long as he was so bound. And he vaguely offered support.