From PathfinderWiki

The Witchcaves are a series of deep caverns in the south eastern region of Irrisen's Hoarwood province. According to legend, great power lies in these caves, which are also suspected of having an entrance to the Darklands.

In 3937 AR the survivors of the failed Harcatha Rebellion fled to the caves in the hope of recruiting Darklands allies to help their cause. Nothing more was heard of them until 4079 AR, when an insane force of Jadwiga emerged from the caves and rampaged across the region until they were wiped out by Irriseni forces led by General Chernim Karina.

Queen Karina, Irrisen's then ruler, ordered the caves sealed. However, a few adventurers recently defied the ban and investigated the caves – and found them overrun by qlippoth. The leader of these fiends is an augnagar called Ulkrostaz. Some of the Harcartha who entered the caves still live, serving as breeding stock and subject to ongoing torture.123