Kezan's Unstoppable Taint

Kezan's Unstoppable Taint is the Zandalar Tribe necklace for warlocks. The item is part of the armor set called Demoniac's Threads. This item is the last in a series of three upgrades. When a warlock reaches a friendly reputation with the Zandalar Tribe, he may receive the weaker, Rare item called Kezan's Taint by speaking to Al'tabim the All-Seeing for a free quest. At Honored, the item can be upgraded to Epic quality and at Revered it can be upgraded further. Each upgrade is a quest reward which also results in more reputation gains and gold.

Source
At, Al'tabim will upgrade Kezan's Taint (revered) in Kezan's Unstoppable Taint (quest).

In the RPG
"A shrunken head with red glowing gems set in its eye sockets hangs from a leather strap of humanoid skin. The skin is blackened and wrinkled. Its oily hair is long and stringy."