Leggings of the Forlorn Vanquisher

Leggings of the Forlorn Vanquisher is a tier 11 armor token. It can be exchanged at in Stormwind City or  in Orgrimmar for the following items:
 * Firelord's Leggings (heroic)
 * Magma Plated Legguards (heroic)
 * Magma Plated Legplates (heroic)
 * Stormrider's Leggings (heroic)
 * Stormrider's Legguards (heroic)
 * Stormrider's Legwraps (heroic)
 * Wind Dancer's Legguards (heroic)

Source
This item drops from Maloriak in Blackwing Descent on Heroic mode.

It can also be purchased from the following vendors for :
 * in Stormwind City
 * in Orgrimmar