The cultist starts off by warping to a new location and then unleashing one of its three attacks: A burst of three homing fire balls which will explode on impact, an ice ball which emits ice shards in six directions as it flies, and an energy orb which fires bolts of lightning to player. These are Lunatic Cultist's direct form attacks.
As Lunatic Cultist gets damaged, it will begin attacking with two spreads of five destructible ancient light projectiles as part of his previous cycle.
Occasionally, Lunatic Cultist will attempt to spawn illusory duplicates of itself, unless the summoning ritual is interrupted by attacking the Lunatic Cultist and not one of the illusions. The Lunatic Cultist will have a golden stripe on his head piece, and a shine in his eye (causes an 'L' shape), where as the illusions won't. A hunter potion can also be used to avoid confusion as it will not highlight the fake cultists. These phantoms will stay, flying in formation and adding their homing Shadowflame attacks to Lunatic Cultist's. This will also result in the summoning of a Wyvern-like Phantasm Dragon, and if there is already a Phantasm Dragon present, an Ancient Vision, which looks like a miniature version of the Moon Lord's head. These phantom duplicates can be eliminated by interrupting the ritual again, but if not, the Lunatic Cultist can amass a large quantity of phantoms, making the fight much more difficult.
The Lunatic Cultist will go through an attack cycle between each summoning ritual, performing four or five attacks before proceeding. This cycle is repeated throughout the battle, and can become chaotic unless the Lunatic Cultist's summoning rituals are properly interrupted.
Also, in Expert Mode, the Lunatic Cultist will spawn ancient devices which shoot 4 purple projectiles after a while.
- This is the smallest boss in the game, being only 3 blocks tall (the size of The Player and most enemies in the game). Because of this, it is recommended to use homing weapons or Yo-Yos if possible.
- If the player fails the battle, the Cultists will not re-appear until the next in-game day.
- "Cultist" is a portmanteau of the suffix "-ist", and "Culto" which is Spanish for worship. "Lunatic" is more likely referring to him worshipping the Moon Lord, although it's also correct to say he's insane.
- There is a Treasure Bag that is supposed to drop from the Lunatic Cultist, but it is currently only obtainable by either third-party tools or, very rarely, free-item servers. There is likely a planned item for Lunatic Cultist but was scrapped.
- If you make any of the cultists despawn, the Lunatic Cultist will not be able to spawn (fixed by restarting the game).
- Added to the game.