The Adeptus Mechanicus built a fortress around the ‘haunted’ caves of Giridium. During the manifestation which occurs every equinox, the Tech-Priests blasted apart rank upon rank of Daemons. The process was repeated for nine long years. Just as the Adeptus Mechanicus were compiling reports and preparing to withdraw, the sky above yawned wide and disgorged a rain of capering, whirling flame-daemons. The ensuing battle raged for months, and when a new wave of blood-horrors burst from the caves at the next equinox, the combined daemonic onslaught saw the Cult Mechanicus slain to a man.