The first layer of Carceri, and the most prominent, Othrys is the exiled home of many displaced figures, most prominently the Titans defeated by the Olympian pantheon ages ago in the great Titanomachy; their great marble temples, though crumbling out of disrepair over the millennia from a lack of local materials, are a prominent symbol of Carceri. Showing to many how even in exile, one can reach great heights, not just survive after being banished from ones' home but thrive. A land alternating between thick swamps and tall mountains, dotted in the few dry lands between by a few small settlements of dispossessed individuals and banished traitors alike.
Othrys is the layer of those who turn against king and country, who forsake their leaders not in the name of justice or other more noble goals, but out of pure self-interest. As such, it is also the natural home for many cells of the Revolutionary League; the largest outpost of Anarchists, the Bastion of Lost Hope, is one of the few major settlements of the layer, oddly open to outsiders — many planars with no connection to the faction call it home. Of course, holding such a population makes it much easier for Anarchists to blend in, as even here any individual may or may not be a member of that faction.
Unlike the other layers, there are few natural hazards to worry about in Othrys. To be sure, the swamps and mountains both can be quite dangerous. In the swamps, one finds great patches of quicksand sometimes nearly a half-mile deep; hordes of mosquitoes, biting flies, and other disease-carrying creatures; any number of beasts eager to taste the flesh of the unwary (including a tenacious population of Prime-born trolls brought to the plane some time back); and enough branches and tributaries of the River Styx flowing through channels carved out by erosion since the dawn of time that it's nearly impossible to tell what water is safe to drink. And most of the plane's most accessible mountains are claimed as sovereign property of the Titans, not a group to be taken lightly. Still, both these dangers are quite ordinary compared with what lies below in Carceri.
Instead, most of the danger here is far more subtle. The petitioners of Othrys can be quite risky to deal with, beings that after many decades or centuries of living in Othrys are entirely absent of trust due to the constant politicking, double-dealing, and backstabbing that is common in all petitioner villages of the layer; there are so many levels of backroom dealings amongst Othryn petitioners that a basher can hardly even say hello to one without offending a half-dozen others, and yet somehow they keep them all straight. And in fact, the layer itself encourages such an attitude. As on the other layers, Carceri provides a natural defense to those that dwell upon Othrys for long enough; here, that takes the form of an enhanced ability to think. After a week or two on the plane, one finds their natural intelligence boosted (+2 to Intelligence after 10 days), but with an inclination to use this intelligence to the benefit of themselves first above all. An attitude that, while perhaps selfish, is almost necessary for survival. Somewhat unfortunately, both this boost of the mind and these mental tendencies are temporary, fading after only a few days of leaving Othrys. Many sages have attempted to find a way to capture this facet of Carceri, with or without the somewhat paranoid side effects, but none so far have succeeded.
- Manual of the Planes, 3rd edition, pg.105
- Planes of Conflict - Liber Malevolentiae, pp.14-19