Source: The Worldwound, pg(s). 9
Shadow Spring is one of the northernmost hot springs in the Frostmire Fen, which can be found in the region of the Sarkoris Scar known as Frostmire. A small village of degenerate humans surrounds Shadow Spring (the village and the spring share the same name), populated by the descendants of evacuees from the nearby city of Dyinglight.
The villagers of Shadow Spring are the descendants of a small group of Kellid men and women who fled the city of Dyinglight following the opening of the Worldwound portal in 4606 AR. Unlike the majority of the city, Shadow Spring's ancestors chose not to flee their crumbling nation, instead settling in one of the more distant sulphurous hot springs that dot Frostmire Fen. They were led there by the Tarnshiav family, one of the most prominent of Dyinglight's aristocracy. The Tarnshiavs still rule Shadow Spring today, but its inhabitants have been greatly changed by the foul Abyssal emanations that blanket this cursed part of Golarion.
Decades of exposure to the evils of the Worldwound wrought permanent changes upon the human inhabitants of Shadow Spring. Most of them are quite insane and practice a form of cannibalism in which they consume the bodies of their dead, along with those of any unlucky treasure seeker who have the misfortune of stumbling into their wretched hamlet. Their insanity quite likely stems from the consumption of animals and plants infected with the demonplague, which was endemic everywhere in the Worldwound. Despite their constant exposure to this disease, the inhabitants of Shadow Spring are strangely immune to its immediate effects, even though they surely carry the disease themselves.