The Screaming Cavern

"You cannot find a Pathfinder worth their salt who hasn't heard about the Screaming Cavern. No one knows what causes the screaming, but all the locals have their own stories about the source of the scream."
~Pathfinder Sullivan

Summary

There are many myths surrounding the Screaming Caverns from the local clans of the Verdant Jungle. The myth accepted by the civilization outside of the Verdant Jungle stems from, the now dead, Hikblip tribe of the Stagnant Moor. The Hikblip tribe believed that the Screaming Caverns was the path to the afterlife, and the screams behind heard were the souls of all the dead being judged by Zelt Shepard of the Dead.
It was forbidden to enter the Screaming Caverns; lest your soul is collected and judged by Zelt before your time. Those who defied the warning were never seen again, driven mad by what they found, or came back emotionless and unresponsive to physical stimuli. These cursed ones were called Koros and executed, or banished from the tribal lands. The Hikblip believed that during Apophrica the Screaming Caverns would unleash the dead souls of the unworthy of Paradise or Tartarus onto the Material Plane.
When the Pathfinders' inevitably stumbled upon the caverns the Hikblip tried to warn the travelers of the dangers. Ignoring them the Pathfinders stumbled into the caverns and succumbed to the curse. The Koros attacked the Hikblip leaving no survivors from the assault. The only Pathfinder not to enter fled the expedition and informed the Council of Exploration and Discovery of their findings.
The Council attempted to keep it under wraps but the events, though muddled, leaked to the populace. The myth of the cursed Screaming Caverns eventually spread like wildfire. Now all Pathfinders' see it as a challenge to enter the Screaming Caverns and discover what's at the end of it.