Tormentors of Torghast in WoW is new event found in The Maw added in Patch 9.1.
Tormentors of Torghast WoW
As you find yourself trekking through old and new portions of The Maw, you may see a double-crossed swords icon on your map titled "Event: Tormenters of Torghast."
The mobs that make up the Tormentors give you an idea of what you are to see in 9.1's version of Torghast.
Upon reaching the location on your map, you will be greeted with a "fill the bar" objective to slay some of the Tormentor's mobs. Once the bar is filled, the Tormentor of that given objective will spawn, a much harder enemy than the mobs you had just slain to fill the bar.
Slaying the Tormentor will grant the player 75 Soul Ash, an important material to craft your legendries, a Bahmeht Chain Link, which when 200 are gathered you combine them to get the Bahmehtra mount.
Additionally, once killing a Tormentor you get Tormentor's Cache, a chance to contain a Warped Phantasma, a weekly reward you can hand to Ve'nari for a nice chunk of reputation and gold.
If achievements are your thing, slaying all fifteen of the unique Tormentors grant you the achievement "Minions of the Cold Dark."
Happy hunting out there on Korthia.