This item is acquired in-game. See its sources below.
In the Appearances collection, Replica Field Marshal's Satin Mantle is listed as Vendor. Appearance ID: 5168. 1 other item wears the same appearance:
Replica Warlord's Satin MantleRead from the World of Warcraft client build files.
Cloth is the armor type Mage, Priest and Warlock wear. With Intellect, Replica Field Marshal's Satin Mantle suits Discipline, Holy and Shadow Priest; Arcane, Fire and Frost Mage; Affliction, Demonology and Destruction Warlock.
Replica Field Marshal's Satin Mantle is part of the transmog set Field Marshal's Raiment (Priest only). The other 14 pieces:
Chancellor's Mooncloth Cowl
Chancellor's Mooncloth Legguards
Chancellor's Mooncloth MittsChancellor's Mooncloth Shoulderpads
Chancellor's Mooncloth VestmentsChancellor's Satin GlovesChancellor's Satin HoodChancellor's Satin LeggingsChancellor's Satin MantleChancellor's Satin Robe
Replica Marshal's Satin Sandals
Replica Marshal's Satin Gloves
Replica Field Marshal's Satin Vestments
Replica Field Marshal's HeaddressBuilt from the World of Warcraft client build files and recorded Auction House snapshots.
Replica Field Marshal's Satin Mantle is not traded on the Auction House, so it has no live market price. It is acquired in-game from the sources listed above. This page collects its first-party game data (identity, effects and where it comes from) from the official World of Warcraft client build.
TheWoWDB