Bolts of Soulcloth are made by tailors by infusing Netherweave with the essence of souls found in Karazhan. They are used in items with high arcane resistance.
Unlike other fabrics, Soulcloth only exists as bolts, and not as individual pieces of cloth.
It is used in the production of the Soulcloth Embrace set, which is moderate-arcane-resistance, multi-purpose gear designed for fights against arcane bosses where the player does not want to reduce their stats excessively.