The game's collection data lists Nullification Greathelm as sold by a vendor NPC in Warspear.
Vendor
Zone
Map
Waypoint
Other items it sells
NPC #88569
Warspear
-
-
166
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).
Read from the World of Warcraft client build files (JournalEncounterItem, JournalEncounterCreature, Achievement) and the Blizzard Game Data quest API.
How Nullification Greathelm Compares
Who It Suits
Plate is the armor type Death Knight, Paladin and Warrior wear. With Strength or Intellect, Nullification Greathelm suits Arms, Fury and Protection Warrior; Holy, Protection and Retribution Paladin; Blood, Frost and Unholy Death Knight.
2 other items in the current build are also called Nullification Greathelm. 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 87024 (87019 to 87029) were usually added in the same batch as Nullification Greathelm: the same quest line, zone, vendor or reward set.