Hive Thetus Crusade
On the planet Neveria II a small-but-dangerous cult of heretics had to be removed. An investigation by an agent of the Ordo Hereticus and a covert strike by the Deathwatch discovered the influence behind the cult: a broodlord had managed to infiltrate and infect the minds of a large group of inhabitants of Hive Thetus. This combined with years of crossbreeding had produced physical and psychic abominations to Mankind.
It became obvious that Hive Thetus was becoming a staging ground for a dreaded Tyranid vanguard force. The Xenos influence had to be removed and the Hive had to be cleansed. The Black Templars called to the challenge of returning the Emperor's Light to Hive Thetus with righteous zeal.
The Broodlord and its followers hid themselves deep within the Hive's blackened depths. It would take some considerable time and effort to removed them. The labyrinth of tunnels, accessways, ducts, and forgotten cities proved to be a deadly and unique battlefield. It was here that the Black Templars fought terrifying battles in cramped corridors against the Tyranid menace. Slowly and at great cost, each sector was cleared from the bottom up. Hive Thetus, and the entire world of Nevaria II with it, was made relatively safe thanks to the efforts of the Black Templars.