From PathfinderWiki

Thraxnorni, also known as the "Bone Caverns" are a series of caverns that sprawl beneath Iobaria's Fangard Forest. A cairn located a short distance away from a crossroad of the Koloran Roads within the forest marks the entrance to the caverns, though other sinkholes that lead to their dark depths are thought to exist. The caverns get their name from stories that say they are lined from floor to ceiling with bones, the victims of the undead and other menaces that dwell within.1


  1. Steven Schend. (2010). Iobaria Gazetteer. The Varnhold Vanishing, p. 63. Paizo Publishing, LLC. ISBN 978-1-60125-234-0