Mage Clan Wars
From Diablo Wiki
The Vizjerei clan used a few umbaru clans from the Teganze jungle areas to create goatmen for their war effort. The plan backfired when five of those umbaru clans turned against the Vizjerei in the war. After decades of fighting, the umbaru clans warring captured a Vizjerei sorcerer, and helped them take control of all goatmen, as well as transformed the five warring umbaru clans into goatmen themselves to defeat the mages. The demon Zagraal was somehow involved in this transformation, and after the war, the goatmen found themselves in servitude of the demon, killing and plundering in his name until the umbaru Witch Doctors killed Zagraal.