The Cult of the Lidless Eye is a canker within the heart of the Mechanicum itself. Deep beneath the surface of Mars the Cult of the Lidless Eye excavates lost technology and experiments with new. The Dark Mechanicus of the Lidless Eye have been present since the civil war on Mars during the Horus Heresy. They venerate Horus as the Great Liberator and wear his symbol to show there devotion to the uncompromising search for knowledge that the Emperor attempted to curtail with his dictates against certain studies, such as the search to create a working AI. Because of the age of the cult few suspect that they are indeed Dark Mechanicus, but nothing could be further from the truth.