The Temple of Lost Souls, known in Rakatan as Urati Kazinal, was a temple built on Lehon inside a dormant volcano named Mount Kazinal ("the mountain of lost souls"). The temple was believed to have been constructed sometime before the collapse of the Infinite Empire in 25,200 BBY as a prison by an unknown Rakatan daritha (or emperor) whose spirit still guarded the entrance to the forgotten temple in 29 ABY.
At the heart of Urati Kazinal, inside the core of Mount Kazinal, rested a sacrificial chamber where countless thousands of condemned Rakata and their numerous slave races were ritually executed, their souls ripped apart and forever sealed within a sphere of dark side energy. Eventually, after the Rakata began to lose their connection to the Force and their slave races rebelled against them, the Temple of Lost Souls was forgotten entirely, laying dormant for the next twenty thousand years.
Sometime after the ascension of Marka Ragnos to the throne of the Sith Empire in 5,100 BBY, the reclusive Sith Lord Urias Orian found his way to Lehon courtesy of the Star Map he had discovered inside the ruins of what became the Temple of Orian on Sepros. It was Urati Kazinal—specifically the sphere of energy which Orian discovered within Kazinal Core—that provided the immortality-obsessed-Dark Jedi Lord with the knowledge he needed to finally imbue himself with everlasting longevity. It was this knowledge that led him to sacrifice the Ombi race of the Sepros system, destroying their life-giving crystal, the Star of Ombus, which so closely resembled the sphere at the heart of Urati Kazinal that had been created by the ancient Rakatan daritha. However, in the end, Orian, the so-called "Immortal", failed in his ambition when, as had happened to the Rakata before him, his Ekind slaves rose up and turned on him, led by their Dark Lady Hafalia Seprosin Chunasca, culminating in the Sith Lord's destruction.