Mirrorghast

Mirrorghast is a Hard Mode boss that can be summoned with a Curse Mirror or waiting for the message “You feel a presence watching in another dimension...” in the Marble Biome. It acts similar to The Brain of Cthulhu but stronger and has different mechanics.

First Phase
It first starts off teleporting around the player and shooting mirror shards at the player. Then a little while later it summons 50 - 60 Cursed Mirrors to attack the player.

Second Phase
After all of the minions are defeated, the boss stops teleporting and dashes towards the player, inflicting the Confused de-buff when hit. It also shoots mirror shards more often and widely with stronger damage.

After getting it to zero health, it will disappear with a message saying “Mirrorghast has been defeated!” And “It’s not over yet, kid...”.