Primal Nether

Primal Nether is used in epic level Engineering, Blacksmithing, Enchanting, Jewelcrafting, Leatherworking, and Tailoring recipes.

Source
This item is a guaranteed drop from the final boss of every 5-man instance on Heroic mode. It also has a low chance to be an additional drop from the final bosses of high level dungeons.

This item is also sold by G'eras in Shattrath City for.

Tailoring

 * Battlecast Hood
 * Battlecast Pants
 * Black Belt of Knowledge
 * Boots of Blasting
 * Boots of the Long Road
 * Girdle of Ruination
 * Golden Spellthread
 * Manaweave Cloak
 * Resolute Cape
 * Robe of Eternal Light
 * Runic Spellthread
 * Spellstrike Hood
 * Spellstrike Pants
 * Sunfire Robe
 * Unyielding Girdle
 * Vengeance Wrap
 * Whitemend Hood
 * Whitemend Pants