The Cleansing of Hive Thetus was a miltary campaign against a Tyranid Genestealer Cult discovered by the Imperial Inquisition to exist upon the Hive World of Nevaria II and ultimately successfully purged from existence by the Black Templars Chapter of Space Marines. The Black Templars were called upon to aid in the extermination of a small-but-dangerous heretical cult on the Hive World of Nevaria II. This menace was investigated by an agent of the Inquisition's Ordo Hereticus working within the overpopulated levels of Hive Thetus, a Nevarian hive city. Soon, this agent discovered the towering spyres of Thetus held a more sinister secret than anyone had at first suspected. A powerful and malevolent influence was behind the spread of the cult's influence.