AGATHYS

The lowest and smallest layer of Carceri is Agathys, and unlike the other five a single orb serves as the only destination within the confines of its limitless darkness. Agathys is frozen solid, an icy sphere of black cut through with streaks of crimson like blood vessels. Anyone doomed to Agathys is frozen forever in its depths, and in many places on the surface of the orb, faces and bodies can be seen in the ice.

Little is known about Agathys. Some planar scholars say it is the actual frozen heart of Carceri, which does operate much like a living creature on a massive scale. Others say the ice is the result of some ancient power of death known as the Reaper, and certainly there is some evidence to suggest this is at least partially true. One of the few known sites on Agathys is the Citadel of the Reaper, a long tower with cavernous tendrils cut into the frozen ground, where death stalks the halls.