Cathrys is a layer of duality, each with its own unique dangers to the unwary. The second layer of Carceri, it is home to the bestial, those that have betrayed their own civilized means and descended to a far baser form of existence, those that believed life would be simpler without the trappings of civilization and social mores. The natural hazards of Cathrys serve well to show such a life is far harder than they would wish. The jungles of Cathrys where the most barbarous tribes dwell, the ultimate nomads that bed in a new place every night, are rich with Tartarean acid that leaves one struggling to make do with a lifestyle of hunting. It saturates the water, the plants, and even the air (1d4 points of acid damage per minute of exposure to the air, with some plants providing greater damage). The plains are somewhat safer; the air itself doesn't try to stick you in the dead book, but the razor-sharp blades of grass can slice a person's legs to ribbon if they don't step carefully (1d4 damage per round when hustling or faster, DC 20 Reflex save to avoid); of course, a somewhat more relevant danger for the relatively peaceful, always moving nomadic "villagers" in these regions. Thankfully for both, those that truly adjust to this way of life eventually grow a protective "skin" of slime and filth, which protects from both the local acid and the razorgrass in the fields.
Oddly enough for a lower plane, the fields of Cathrys are quite livable. No permanent villages can be found here, only the moveable settlements of the nomadic petitioners, passing through and remaining in a given place only until it's been hunted out and polluted beyond livability; of the species represented amongst them, humans and hill giants are perhaps the most common. So long as one avoids the Steading, keeps a good distance from the jungles, and is careful about the razorgrass, travel through these parts of Cathrys can be almost peaceful. And though the locals loathe anything more civilized than a campfire, trade caravans through Cathrys are fairly common as a result. Even the Blood War rarely touches upon Cathrys, largely because it serves as quite the annoying battlefield for the weaker fiends and mortal mercenaries that make up the bulk of the fighting. Occasionally aerial battles will occur here, but such battles are rare as it is.
This is, of course, not to say Cathrys is benign, for its jungles hold any number of threats. The jungle's petitioner tribes are certainly nothing to ignore; murderous, cannibalistic men and women that have drifted so far from civilization, they've abandoned even the concept of language. Not limiting their attentions to outsiders, they raid travelers and plainsmen alike, with even the nomads not safe from their rapacious onslaughts. However, they are far from the most dangerous threat, for Cathrys is the native home of both the gehreleth and the vaath, two of Carceri's best known native peoples and two of the most dangerous. A sensible visitor will avoid even setting foot in Cathrys's jungles, but unfortunately some times this cannot be avoided; while Cathrys's peaks are almost always located amongst the savannahs, its chasms quite often are within the forested depths.
- Manual of the Planes, 3rd edition, pg.105
- Planes of Conflict - Liber Malevolentiae, pg.19