The Cabal is a dark cult that is a sub-organization of the Shadow Council which operates exclusively in Outland. They are led by Grandmaster Vorpil and Blackheart the Inciter. The organization's members have holdings in the Bone Wastes and external ruins of Auchindoun in Terokkar Forest and in the Shadow Labyrinth of Auchindoun. These cultists are said to have summoned the evil entity, Murmur which in turn caused the explosion which destroyed the necropolis of Auchindoun and flattened the surrounding forest, creating the Bone Wastes.
The evil being they summoned proved too hard to control and many are now fleeing Auchindoun. Several have gathered in and around the Shadow Tomb where they are storing artifacts of power they took from Auchindoun. Among these are the sacred 
[Drape of Arunen], 
[Gavel of K'alen], and 
[Scroll of Atalor] which belonged to powerful draenei patriarchs of each item's respective namesake. The Cabal has also taken Akuno the Broken, friend of Mekeda, hostage within the Shadow Tomb.
Ner'zhul once fled to find shelter in Auchindoun when he was being hunted by the Alliance forces under Danath and Thalressar. It was in Auchindoun that Ner'zhul found the Cabal, and informed Vorpil of the treachery of the Shadow Council. Vorpil pledged the Cabal to Ner'zhul. Danath, Thalressar and their forces managed to launch a surprise attack on the Horde and the Cabal. Vorpil and Blackheart took refuge in the deeper tunnels of Auchindoun, and the Alliance left them to their own devices once Teron Gorefiend ported the leadership echelon to the Black Temple.