The Styx (/stɪks/; Ancient Greek: Στύξ [stýkʰs], "Hate, Detest") is a river in Greek mythology that formed the boundary between Earth and theUnderworld (the domain usually called Hades, which is also the name of its ruler). The rivers Styx, Phlegethon, Acheron, Lethe, and Cocytus all converge at the center of the underworld on a great marsh, which is also sometimes called the Styx