Stolen Crystal Heart盗まれた結晶の心臓

A giant ancient gemstone that mutated its holder into a monstrosity. It originally belonged to the Hive Mother, but was ripped out by a power-hungry caveling.
In-game description

How to use Stolen Crystal Heart

Stolen Crystal Heart is the key for the Malugaz statue to the right of the Core.

Use (insert) it on the Malugaz statue to the right of the Core.
The statue comes to life. Once all three statues are active, you can move on past the Great Wall.

Activating this statue also unlocks extra goods at some merchants (in the game data, some merchant items require this statue to be active).

How to get Stolen Crystal Heart

Defeating Malugaz the Corrupted always drops it (1)

Scene containers, dungeon placements, guaranteed drops and natural spawns are based on the Obtaining data of the Core Keeper Wiki (Fandom) (CC BY-SA 3.0), because these are not in the game files this site reads. Scene names are the wiki's English names.