Long ago, when the Zygarian Empire invaded Jamul with its armies of chariots and wyvern-mounted knights, the Lord Xulthan's castle in the Painted Hills was one of the last to fall. Protected by flying knights of his own, and a sorcerer of legendary strength, Xulthan was able to drive back wave after wave of Zygarian troops.
Xulthan's sorcerous ally was sacrificing the souls of the people of the fortified city to power his battle magic spells. When this was discovered, even his mighty spells were unable to protect him from the vengeance of the mob. He was torn apart in a riot that set half the city on fire, and what this attack didn't destroy, the Zygarians did, with catapult, sword, and fire.
When all of Jamul had been conquered and subdued, the Zygarian governor of the central realm returned to the site of the razed castle in the Painted Hills. He put the surviving inhabitants to work quarrying the red, blue, and cream-colored stones of the layered hills to build a new fortress. Governor Malokor had his own sorceress, and the blessing of the God-Queen, so his power was immense. The Castle rose swiftly with the aid of Demons and Spirits of the Outerdark.
Upon its completion the price of the assistance of the demons was levied upon the workers. All were slain in a tremendous sacrifice to forge a spell of invulnerability upon the fortress. But something went terribly wrong, or was subverted by the Chaos of the demon slaves, for the castle became not only impregnable, but immaterial.
The physical form of the castle was shifted to another dimension, adjacent to Weirth, where the Governor and his cursed followers dwell to this day, as shades and ghosts and worse. Today, when the stars are right, or the rituals have been performed, the castle can materialized upon the hills of Weirth and the accursed Governor and his henchmen ride forth to hunt. They search for more souls and more blood to reverse the ritual that has cursed them to the half-existence in the otherworld.