From Lexicanum

The Heart of Blood is one of the most favoured Daemon avatars of the Blood God Khorne, and piled legions of skulls for its master. It has the power to summon bloodstorms, which drains blood from its victims without the need to strike a physical blow. It forged for itself a suit of armour which contained all of its hate, malice and cunning. Its greatest rival is the Omphalos Daemonium, which it trapped within the heart of a Daemon Engine. However, the Heart of Blood too became imprisoned by the Iron Warriors, and was forced to create and sustain an unbreakable psychic barrier around the fortress of Khalan-Ghol for over ten thousand years. ¹

Sources

• ¹:Dead Sky, Black Sun (Novel)