Lunatic Cultist

The Lunatic Cultist is a Hardmode, post-Golem boss summoned by killing all four Cultists that spawn at the Dungeon's entrance after Golem is defeated. Beating the Lunatic Cultist initiates the Lunar Eventsit can also be spawned in hardmode

Behavior
The boss only has one defined stage, but its attacks become progressively stronger as it loses health. During the fight, it flies around at random, firing lightning, fireballs, shadowflames, exploding packed ice, and two volleys of five destructible stardust projectiles each.

It will often project illusory duplicates of itself, only one of which can be attacked to deplete the boss's health. These illusions are summoned one by one, and can be prevented by damaging the Cultist enough while summons them. The illusions are semi-transparent, which makes it easier to tell them apart.

Each time the player attempts to attack one of these illusions, the Lunatic Cultist summons a Phantasm Dragon, a Wyvern-like enemy, to attack the player. If the Phantasm Dragon is not defeated and the player attacks another duplicate, an Ancient Vision, which looks like the head of the Moon Lord, will be summoned.

to avoid the cultist summoning the phantasm dragon hit the original cultist not the copies

Tips

 * Avoid defeating the Lunatic Cultist if you are not yet ready for the Lunar Events, as after beating the Cultist the Lunar Events begin immediately, and there is no way to de-summon them (aside from defeating them).
 * Shooting the decoy cultist is not a bad idea if you have vampire knives. The Phantasm Dragon is very long and you can easily regain some life by hitting the Dragon with a wide barrage of knives.

Trivia

 * Its lightning attack seems to be fired from a giant and immobile Magnet Sphere.
 * Its lightning attack also seems to be a reference to an attack used by Agahnim in The Legend of Zelda: A Link to the Past.
 * The packed ice it fires is similar to that of the Ice Queen.
 * It appears visually similar and may be a nod to Crowno, an artist at Re-Logic, and his vanity set. However, the opposite may be true as well.  The set has been likened to a plague doctor costume, a garment worn by physicians who treated the Black Plague in the fourteenth century C.E.
 * It is the smallest boss, the only boss without an awakening message, and the only character in the game that speaks (it says "How do you know" when summoned).