Glass Soul

The Glass Soul is a post-Moon Lord accessory that causes the player to die instantly when getting hit. Wearing the item also gives the player 100% increased damage, as well as disabling shadow dodge and killing the player no matter how many revival effects are active.

Defeating Abaddon, Araghur, The Lost Siblings or Erazor in True Mode with the item equipped will reward you with Glass Hearts.

Trivia

 * This item is a reference to a modded gamemode of the same name for Hollow Knight, in which you permanently die when taking a single hit.