Styx

In Greek mythology, Styx, also called the River Styx, is a goddess and one of the rivers of the Greek Underworld. Her parents were the Titans Oceanus and Tethys, and she was the wife of the Titan Pallas and the mother of Zelus, Nike, Kratos, and Bia. She sided with Zeus in his war against the Titans, and because of this, to honor her, Zeus decreed that the solemn oaths of the gods be sworn by the... (Wikipedia)