Leggings of the Incarnate

Leggings of the Incarnate is the Tier 4 cloth legs armor for shadow priests and gives bonuses to stamina, intellect, spirit and overall spell damage. It is available through token item that drops in Gruul's Lair.

Source
This item is sold by in the Seer's Library on the Scryer's Tier and by  in the Shrine of Unending Light on Aldor Rise in Shattrath City. The cost of the item is a token.