Garvok, like it's swordkin, was forged by it's respective Rune Lord using one of the Primal Sins of mortal-kind; the sin of Wrath tapping into the very nature of sin and reality itself. It is said that the Alara'hai were forged at the place where consequence and reality met. Use of such a force which is Primal, Eternal and with a nearly Infinite capacity was a clear affront to all Gods with the exception of only the most Chaotic and Malevolent beings. As with the other Alara'hai, the sword was said to be completely indestructable for as long as Wrath existed, so too would Garvok.
The sword was said to bind to it's weilder for life, enslaving them to the sin of Wrath until their individual personality was consumed and their life transformed into one of the utter and single minded pursuit of the sin to which they were bound, Wrath. Ancient tales abound of mighty heroes coming into possession of one of these swords only to be possessed by it, becoming single minded servators of their vaunted weapon.