From PathfinderWiki
(Abyssal realm)

urban, ruins, burning forest, volcanic wasteland
A chunk of Hell ripped out and placed next to Lamashtu's realm of Kurnugia

This unusual layer of the Abyss was originally part of Hell. Lamashtu struck a deal with the four demigods known as the Goblin Hero-Gods, and siphoned their home into the Abyss and placed it next to her own realm of Kurnugia.

This strange history is evidenced by the various ruins of Basalfeyst, which are in the architectural style of Avernus. Intact buildings are a bizarre mix of demonic, devilish and goblin styles.

Each of the four demigods, Hadregash, Venkelvore, Zarongel and Zogmugot, has their own region.

The other main feature is the Screaming Pyrelands, an ever burning forest. It is said that the heart of every tree is the imprisoned soul of a goblin who remained loyal to Asmodeus rather than switch allegiance to Lamashtu, condemned to burn in agony for all eternity.

Other unclaimed territory consists mainly of volcanic wastes and plateaux.1

Goblins believe their heroic deeds will bring them to Basalfeyst on death to serve their masters; they also believe that if they fail they will also come to Basalfeyst as food for the Goblin Hero-Gods.2