Replacing the traitorous Emperor's Children as the IIIrd Legion, the Black Templars Legion was a Second Founding successor to the Imperial Fists, formed from those few of Dorn's sons who objected to the tenants of the Pricipia Belicosa. As such, the structure of the Black Templars deviates quite considerably from that of a typical Principia-adherent Legion. The Black Templars are an extremely zealous Legion, some would say to a fault. Even before the Imperial Cult became the state religion of the Imperium in the 32nd Millennium, the Black Templars eschewed the use of Psykers amongst their ranks and and persecuted Xenos and traitors with unprecedented tenacity and hatred.
Founded under the leadership of former Imperial Fists First Captain Sigismund, the Black Templars have been one of the most active participants in the Second Great Crusade, hunting down and destroying those who stand in the way of bringing about the great Pax Imperialis Secundus where ever and however possible. For this reason, the Black Templars operate out of a massive "Crusade Fleet" rather than from a traditional homeworld, enabling them to easily mobilize their forces. The Black Templars are also noted for their almost obsessive use of close combat tactics, taking great pride in skill with hand-to-hand weaponry and great pleasure in slaying the foe up close and personal.