A demon-haunted wasteland that lies at the northern-most reaches of central Avistan, the Worldwound is an unnatural blight: it is a rift to the Abyss opened on the Material Plane. It appeared shortly after the death of the god Aroden at the beginning of the Age of Lost Omens, and is probably the greatest threat to life on the face of Golarion.
Unsurprisingly, considering the inherently chaotic nature of demons, the Worldwound has no government and is instead a loose coalition of demonic tyrants with the strength to rule their weaker kin. They are united by one common purpose: to cause as much misery and destruction on Golarion as possible. The country is split into many, many petty fiefdoms, each ruled by a demonic master. Whether they rule through sheer force (as is favoured by the more powerful demons such as balors or mariliths) or through subtle manipulation (favoured by succubi and glabrezus), each realm is its own nightmare, and each is equally hostile to mortal life.
Most of the cities that once belonged to the Kellid realm of Sarkoris now lie in ruin, but some still stand and are inhabited by both humans and demons. Most of the humans fall into two categories: cultists and immoral mercenaries who have joined forces with the fiends, and humans kept as chattel for food or sacrifice. A few human settlements still exist that have managed to withstand the demonic armies, but they are very few in number and have mostly allied with other powers for their protection.
The geography of the Worldwound is a sickening, flexible thing, with the features of the land shifting in front of the viewer's eyes. This fluidity of form grows worse the closer one gets to the actual rift at the center of this region. The thin veil between Golarion and the Great Beyond tears completely there, and demonic monstrosities pour forth unabated from the depths of the Abyss. At the distal reaches of the Worldwound, where it borders on the surrounding realms, this instability subsides.