Heart of Auchindoun

The Heart of Auchindoun is a crystal powering up all of 's defenses. It is made up of four pieces:
 * Karab'uun
 * Sha'tari (item)
 * Auch'naaru
 * An unnamed fourth one, that was safeguarded by the when the  managed to steal the others.

Speculation
Since Auchindoun is powered up by Arkonite crystals from the Jorune Mine, the Heart is presumably Arkonite as well.