1,500 years before the opening of the Dark Portal, the powerful Gurubashi Empire was torn apart by a massive civil war. An influential group of troll priests, known as the Atal'ai, called forth the avatar of an ancient and terrible blood-god named Hakkar the Soulflayer. Though the priests were defeated and ultimately exiled, the great troll empire collapsed upon itself. The exiled priests fled far to the north, into the Swamp of Sorrows, where they erected a great temple to Hakkar in order to prepare for his arrival into the physical world.
In time, the Atal'ai priests discovered that Hakkar's physical form could only be summoned within the ancient capital of the Gurubashi Empire. It was in Zul'Gurub that Jin'do the Hexxer enslaved several high priests of the Gurubashi to aid him in summoning their dread god, Hakkar the Soulflayer, into Azeroth.
In order to quell the blood god, the trolls of the land banded together and sent a contingent of High Priests into the ancient city. Each priest was a powerful champion of the Primal Gods - Bat, Panther, Tiger, Spider, and Snake - but despite their best efforts, they fell under the sway of Hakkar. The champions and their Primal God aspects started feeding the awesome power of the Soulflayer