Heartcore

A Heartcore is a mortal heart that has been transformed into a magical crystal as a result of exposure to demonic magic. They serve as a vital organ for demons, and their food source: a demon can expose a mortal's heart to their own demonic energy to transform it into a Heartcore and devour it. Heartcores can be procured from any mortal creature: while humans provide the best Heartcores, Rip & Tear have procured Heartcores from mice on one occasion.

While demons are able to ingest the same kinds of food as mortals, they do not provide adequet sustainance. Heartcores are their main food source: without them, they grow weak and are less able to recover from serious injuries.

A demon's Heartcore is one of its two weak points, the other being the demon's brain: only through the total destruction of a demon's brain or Heartcore can a demon be slain.