Gothra the Trembler

During the Venthyr Assault, talk to Burly Hurly and he'll throw you to the top of the wall.
Pick up 4 quests from NPCs there and [npc=178228], [npc=178172], and [npc=178066] fly off.

You'll find [npc=178237] again under some stairs across the way.

If you click on him, he'll take you to the top of the stairs where you'll be dropped in front of Gothra the Trembler.

If you have not finished the four quests yet, you cannot do anything. , General Draven flies off and leaves you alone.

Go back and finish the quests, turn them in, then talk to General Draven. He'll fly you back to the top again, but this time he'll stick around.

To defeat Gothra, enter each of the 4 mirrors, turning the spotlights into the mirrors. When you return after the 4th mirror, there will be a short cutscene. Congratulations!

During the event (see vizoere's comment), it's up in the Maw.
TomTom coordinates: /way 28.85 12.04

Currently unkillable as the mirrors are unable to be activated due to a bug.