Haart's cult is a cult that appears in the Playing with Fire campaign in Heroes of Might and Magic III: Armageddon's Blade. It was a necromantic cult that served Lord Haart.
After his death at the hands of Lich King Gryphonheart at the end of the Restoration Wars, the cult disbanded and went into hiding, but later took Haart's corpse and raised him from the dead. Haart then raised the dead members of the cult, and led an army of undead through Tatalia, killing and raising everyone they met.
The leaders of Tatalia were slow to come up with an effective force to meet him in battle, and Erathia was too busy with the Demon Wars to provide much help, so it was up to the fire witch Adrienne to fight them. She was relentless in her counterattacks, and after a long, bloody struggle, the remains of his cult rallied around their leader in a final stand. In the final fight, the cult was eradicated, as was their leader.