Lethe Hades, unlike the rest of the Hades family, was a good person. He had five siblings: Acheron, Phlegethon, Styx, Cocytus and Aornis, all of whom were evil. He never actually appeared in the books, only mentioned in one of the chapter headings, and little is known about him except that he is the 'white sheep' of the family.

Like all the siblings, he is named for one of the rivers of the Underworld.