Layer of Carceri
Orthrys, the first layer of Carceri, is a realm of vast bogs and quicksand. The River Styx runs freely through the layer, saturating the ground with its magic. Channels carved into the soft ground through eons of erosion are wide and deep. Where there is no river, there are swamps. Though patches of dry ground exist, they are rare and usually climb swiftly to rugged mountains where enraged titans dwell. Mosquitoes swarm the air above the bogs, annoying travelers. Even more annoying are the smooth-talking petitioners that populate this dreary realm.
Bastion of Last Hope: A fortress made of black igneous rock squats in a mountain range of Orthrys. The ambient, reddish light of the plane lends the Bastion of Last Hope a brooding air of menace. Only one entrance offers itself, and those entering can't help but notice that the entrance strongly resembles the maw of some massive demonic toad. No one person rules the Bastion. Instead, it serves as a sort of outpost for anarchists. Here a traveler can obtain all manner of forged documents, surgical alterations to aid a permanent disguise, and various other nefarious goods and services. It is a good place to find assassins, spies, and others of ill repute. But cunning travelers remember that they're on a plane full of traitors, so they trust no one within the Bastion's walls.
Mount Orthrys: The highest peaks of the mountain ranges on two of this layer's orbs reach ridiculously high, just bridging the planetary gulf between them. At their intersection is a titanic palace of white marble columns, amphitheaters, and galleries. Here lives a race of titans, banished from the Material Plane long ago. The titan lord of Mount Orthrys, Cronus, resides at the center of his palace in a throne room a mile wide. Visitors may seek audiences with Cronus to hear his wisdom, but those who seek such counsel must be always aware that the titan's eons-long anger at his confinement may lash out unexpectedly at those who can come and go at their leisure. Cronus has the power of a lesser deity for the purposes of altering Mount Orthrys.