Read from the World of Warcraft client build files (JournalEncounterItem, JournalEncounterCreature, Achievement) and the Blizzard Game Data quest API.
How Membranous Slippers Compares
Who It Suits
Cloth is the armor type Mage, Priest and Warlock wear. With Intellect, Membranous Slippers suits Discipline, Holy and Shadow Priest; Arcane, Fire and Frost Mage; Affliction, Demonology and Destruction Warlock.
Transmog Sets
Membranous Slippers is part of the transmog set Threads of Awakening (Priest, Mage and Warlock only). The other 16 pieces:
Blizzard numbers items as they are created, so the named items next to ID 221149 (221144 to 221154) were usually added in the same batch as Membranous Slippers: the same quest line, zone, vendor or reward set.