Demon Soul

From wow.incgamers.com

A strange and powerful artefact originally created by Deathwing and the other Great Aspects to combat the dire threat of the Burning Legion during the War of the Ancients. Each of the Great Dragons imbued the weapon with a portion of their essence, save for Deathwing, who deceived his kin so that he might betray them at a later date.

It was this object that permitted the Orcs to enslave the Dragonqueen Alexstrazsa, and allowed them to subjugate her offspring.

The Demon Soul was destroyed by the mage Rhonin around the conclusion of the Second War, returning the diminished Aspects to their former power.