River Styx

No one knows where it rises and no one knows where it ends, but all the Lower Planes know the River Styx. This wine-dark, rank river bubbles and churns through the top layers of Acheron, Baator, Gehenna, the Gray Waste, Carceri, the Abyss, and Pandemonium. Side channels of this odious river reach to other layers of these planes - the fifth level of Baator and some of the unnumbered layers of the Abyss in particular. The flow isn't linear or predictable, either. On one journey, a boatman goes from Baator straight to the Abyss; on the return, the river shifts its banks and carries the cutter from the Abyss to the furnaces of Carceri. The flow is unmeasured and unmapped.

Where the Oceanus is sweet, the Styx is foul. Its water is black, putrid, and greasy, yet still a temptation to those suffering from thirst on these planes. One taste or touch of its water and a being may suffer total amnesia of his past life, or at the very least the events of the past day. Beneath its sluggish surface, the currents of the Styx are swift and dangerous, often sucking down boats or pulling swimmers under.

Still, the Styx is useful for travel from plane to plane. A journey to any point on its banks never takes more than a day (although it might be a dangerous day). Horrid and fantastic boatmen called marraenoloths ply its waters, their skills supernaturally competent. All of them are willing to carry passengers - for the right price.

Note: The River Styx originally appeared in this form in the Planescape AD&D campaign setting from TSR. Its use here is for the purposes of providing context for the campaign only.