Calamity's Vanities/Mirror Matter

The Mirror Matter is an Expert Mode-exclusive pet summoning item dropped by Ceaseless Void. It summons a small Dark Energy to follow the player.

Trivia

 * The item's tooltip is a reference to the superstition of thinking breaking a mirror results in bad luck
 * The item is a reference to Ceaseless Void's oldest sprite, where it appeared to be a mirror.