The Blackheart Templar was the regime of undead soldiers led by Mauron Alnamis that served as the core generals for The Dark Hand Covenant. The group consisted of approximately twenty members, all of which were soldiers in the army of Stormwind serving directly under Mauron. After the Alliance raided Draenor at the end of the Second War, Mauron's body was completely taken over by the spirit of the orcish warlock Al'Ghul, leader of the Blackheart Clan. He became a manner of Death Knight and developed a tainted aura that corrupted his closest subordinates, transforming them into undead agents. He named them the Blackheart Templar, after his former Blackheart Clan. He made a mission of bringing the Burning Legion to Azeroth, and his Templar followed him unquestionably.
After the Scourge became a devastating force in Lordaeron, Mauron recognized the potential for an alliance with the Lich King's agents and ventured to the Eastern Plaguelands to request an audience with Kel'Thuzad. However, he was never able to merge the Blackheart Templar and The Dark Hand Covenant with the Scourge as he planned, as on the way his second in command, the undead mage Embron, betrayed Mauron and locked his soul away within the bounds of a mystical grimoire. Embron took control of both the Templar and the Covenant and led them away from the Plaguelands, using the groups to fulfill his own ends.