The lower planes (sometimes Lower Planes) is a collective term used in the Great Wheel cosmology model to represent the Outer planes of Evil alignment, located across the bottom of the Great Wheel. These are Acheron, the Nine Hells, Gehenna, Hades, Tarterus, the Abyss, and Pandemonium. The only other thing these planes have in common is the river Styx which flows through at least one level of each Evil plane. The World Tree cosmology model rearranged, renamed, and reorganized the lower planes into the Fiendish Planes but some people still use the older term to describe the evil-aligned planes.