This item is acquired in-game. See its sources below.
In the Appearances collection, Maddening Osmenite Girdle is listed as Profession. Appearance ID: 40986. 2 other items wear the same appearance:
Read from the World of Warcraft client build files.
Plate is the armor type Death Knight, Paladin and Warrior wear. With Strength or Intellect, Maddening Osmenite Girdle suits Arms, Fury and Protection Warrior; Holy, Protection and Retribution Paladin; Blood, Frost and Unholy Death Knight.
Maddening Osmenite Girdle is part of the transmog set Cosmic Aberration's Plate (Warrior, Paladin and Death Knight only). The other 16 pieces:
Maddening Osmenite Legguards
Second Sight Helm
Breastplate of Twilight Decimation
Writhing Spaulders of MadnessPauldrons of Infinite DarknessGreathelm of Phantasmic RealityCarapace of Pulsing Vita
Gauntlets of Foul Inquisition
Dragonbone VambracesDark Crystalline GirdleLiving Obsidian Legguards
Boots of Hallucinatory RealityBelt of Muttering TruthsReality-Defying GreavesSabatons of Malevolent IntentBracers of Phantom PainsBuilt from the World of Warcraft client build files and recorded Auction House snapshots.
Maddening Osmenite Girdle 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