The game's collection data lists Shadowflame Mantle as sold by a vendor NPC in Shimmering Expanse.
Vendor
Zone
Map
Waypoint
Other items it sells
NPC #50324
Shimmering Expanse
-
-
10
Vendor NPC, zone and position come from the client's collection source tables (CollectableSourceInfo and CollectableSourceVendorSparse); coordinates are the in-game map readout.
Build history
First seen in build 5.5.4.69585 (Mists of Pandaria).
In the Appearances collection, Shadowflame Mantle is listed as Vendor. Appearance ID: 14776.
Read from the World of Warcraft client build files.
How Shadowflame Mantle Compares
Who It Suits
Cloth is the armor type Mage, Priest and Warlock wear. With Intellect, Shadowflame Mantle suits Discipline, Holy and Shadow Priest; Arcane, Fire and Frost Mage; Affliction, Demonology and Destruction Warlock.
Transmog Sets
Shadowflame Mantle is part of the transmog set Shadowflame Regalia (Warlock only). The other 8 pieces:
3 other items in the current build are also called Shadowflame Mantle. Same-name entries are usually a different rank, faction, quest stage or reward track of the same object.
Blizzard numbers items as they are created, so the named items next to ID 65263 (65258 to 65268) were usually added in the same batch as Shadowflame Mantle: the same quest line, zone, vendor or reward set.