Read from the World of Warcraft client build files (JournalEncounterItem, JournalEncounterCreature, Achievement) and the Blizzard Game Data quest API.
How Void-Pact Leggings Compares
Who It Suits
Cloth is the armor type Mage, Priest and Warlock wear. With Intellect, Void-Pact Leggings suits Discipline, Holy and Shadow Priest; Arcane, Fire and Frost Mage; Affliction, Demonology and Destruction Warlock.
Transmog Sets
Void-Pact Leggings is part of the transmog set Felfume Raiment (Priest, Mage and Warlock only). The other 16 pieces:
Blizzard numbers items as they are created, so the named items next to ID 128062 (128057 to 128067) were usually added in the same batch as Void-Pact Leggings: the same quest line, zone, vendor or reward set.