Bloodstone Choker

The Bloodstone Choker was a possession of Gakin the Darkbinder before Surena Caledon stole it and joined the Defias Brotherhood. The choker was used to summon a Voidwalker in the quest The Binding (Voidwalker, Stormwind) at the Summoning Circle, in one of the crypts underneath the Slaughtered Lamb. It seems to be made out of Bloodstone.

Source
This item was provided as an objective for The Binding (Voidwalker, Stormwind).