Judging by the general theme of the Mausoleum as well as the summoning animation seen at the start of the battle, it seems likely that The Heretic is a version of The Haunt that has been revived (to an extent) by necromancy.
The second phase has The Heretic coming out of his invulnerability to attack Isaac. 0 Min-Min is a boss added in The Binding of Isaac: Repentance that can appear in Downpour. The Fanatics walk towards Isaac to do contact damage, occasionally firing homing tears. When The Heretic spawns, he will be invulnerable to damage similar to The Haunt's first phase until all the Fanatics have been killed. They are invulnerable until The Heretic appears. The Heretic will always have an arena filled with extinguished campfires, which he uses for one of his attacks.Īt the beginning of the fight, five Fanatics will be gathered around a pentagram circle.