Felcloth

Unlike other cloth items, Felcloth drops from demons instead of humanoids. Felcloth can also be purified to make Mooncloth.

Source
This item drops from level 50-60 demons, most commonly found in the Misty Valley of the Swamp of Sorrows, the Warpwood Quarter of Dire Maul (east), Mazthoril in Winterspring and the Tainted Forest in the Blasted Lands.

Leatherworking

 * Wicked Leather Armor

Tailoring

 * Mooncloth
 * Core Felcloth Bag
 * Felcloth Bag
 * Felcloth Boots
 * Felcloth Gloves
 * Felcloth Hood
 * Felcloth Pants
 * Felcloth Robe
 * Felcloth Shoulders
 * Robe of Winter Night
 * Robe of the Void
 * Runed Stygian Belt
 * Runed Stygian Boots
 * Runed Stygian Leggings

As a quest objective

 * An Imp's Request
 * Hot and Itchy

Places to farm

 * Lvl. 50+: Felwood, just west and north west of Jadefire Run located in the North part of Felwood. (Runecloth also drops here.)
 * Lvl. 50+: From the Felguards (surrounding the Dark Portal) in Blasted Lands.
 * Lvl. 52+: From the Satyrs (Legash Encampment) in Azshara.