Heart of Fury

The Heart of Fury is the red shard of the ata'mal crystal. When possessed by an individual, it accentuates the individual's aggressiveness and strength.

World of Warcraft
The Heart of Fury drops from Shadowlord Deathwail on the Ata'mal Terrace in Shadowmoon Valley as a quest objective for. Its purpose is to be set into the, which was given to high-ranking draenei priests, who would then have complete access to the Temple of Karabor, now known as the Black Temple.

Background
Velen, the draenei prophet, originally possessed the Heart of Fury. When he was captured by Durotan, the crystal was taken from him, along with the Brilliant Star. Ner'zhul's wish was to see Durotan's prisoners, for Velen was not alone when he was taken. Unfortunately for Ner'zhul, Durotan arbitrarily set the prophet free, but not before taking the two ata'mal crystals from him. The Heart was then utilized against the draenei by the Horde in their genocidal onslaught. The crystal was passed amongst the orc clans at each new moon, even coming to Durotan's hands for the orcs' attack on Telmor. It now lies within the possession of the fel orcs in Shadowmoon Valley.