Molten Heart

The Molten Heart is used to make the Melter Core

Obtaining
Molten Hearts are rare loot (5%) in Crimson Piglin Forge, also, you can have it has a rare trade from a Blacksmith Crimson Piglin

Crafting Ingredient
Four Obsidian, three Smooth End Stone, one Nether Star and one Molten Heart = Melter Core

Trivia
The Molten Heart image is a reskin of the Diamond Heart item from Quark mod