Read from the World of Warcraft client build files (JournalEncounterItem, JournalEncounterCreature, Achievement) and the Blizzard Game Data quest API.
How Nightsfall Gauntlets Compares
Who It Suits
Plate is the armor type Death Knight, Paladin and Warrior wear. With Strength or Intellect, Nightsfall Gauntlets suits Arms, Fury and Protection Warrior; Holy, Protection and Retribution Paladin; Blood, Frost and Unholy Death Knight.
Transmog Sets
Nightsfall Gauntlets is part of the transmog set Leyline Defender's Sunplate Armor (Warrior, Paladin and Death Knight only). The other 16 pieces:
Blizzard numbers items as they are created, so the named items next to ID 139056 (139044 to 139061) were usually added in the same batch as Nightsfall Gauntlets: the same quest line, zone, vendor or reward set.
Satchel of BuoysID 139044 · Quest"A satchel filled with leystone buoys."