The Maelstrom's Wrath is a neck piece and one of the Predator's Armor set items. This item is actually the last of a series of three upgrades to a weaker uncommon item called Maelstrom's Tendril. When a hunter reaches a friendly reputation with the Zandalar Tribe, he may recieve the tendril (as well as some additional rep and gold) by speaking to Falthir the Sightless for a free quest. At Honored the item is upgrades to Rare quality and at Revered the Tendril is upgraded further, every time by completing another instant quest (and recieving more reputation points and gold).
At Exalted Falthir will upgrade the Tendril to the Maelstrom's Wrath, and then the item will count toward the set bonus.