The River Styx

Spirits usually arrive in Hades on the border of the river Styx, which has as its tributaries the rivers Acheron, Cocytus, Aornis, the flaming river Phlegethon, and Lethe, whose waters, when drunk, induce loss of memory. The ferryman Charon conveys the arriving spirits across the Styx. They then pass the guardian Cerberus, who can take the form of a gigantic humanoid warrior or of a savage three-headed dog.