From PathfinderWiki

Threshold was a prison tower in the High Cairns of Sarkoris reserved for those who practiced arcane magic. It is now the epicenter of the Worldwound.1


In -1600 AR frost giants from the Northmounds were defeated on the future site of Threshold by Kellids and druids of the Green Faith.2 The prison was built some years later to imprison arcane spellcasters, who could continue their research only under the supervision of druids and other religious leaders. One of the prisoners, Areelu Vorlesh, made a deal with the demon lord Deskari and attempted a jailbreak. This eventually resulted in the Worldwound opening at that very site. Threshold straddles Golarion and the Abyss.13


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