The Cavern of Screaming Skulls was a cave within volcanic Mount Octan, on Fondor's jungle-moon of Nallastia. Hidden deep within the cavern were the fabled Lost Stars of Nallastia, originally brought to the moon by founding colonial leader, the Margrave Octan. Obi-Wan Kenobi, with the help of the Skull Queen (the moon's ruling Margravine, Quenelle), recovered these ancient power gems in 23 BBY, in order to free the parents of Klay Firewell from the life-threatening energy-field of the megalithic Trinity Stones.
The cave received its name from the sounds made by in-rushing wind as it whistled between the ancient fossilized jaws and skeletal bones of Nallastia's native animals and reptiles that perished therein during a volcanic eruption millions of years in the past—long before the arrival of human colonists on the moon. The eruption transformed the creatures' home into a series of massive lava flow tubes, leaving the fossilized forms of their open jaws and writhing skeletons embedded in the cavern walls. The eerie sounds of the wind rushing through the tunnels and chambers, combined with the whistling of their skeletal remains, produced bone-chilling sounds resembling the howls of wounded, dying creatures.