Requirements:
Engineer with Goblin Glider tinker.
Bottled tornado from the rare Kal'tik the Blight.
You will first start in this spot and use your Bottled Tornado.
https://i.imgur.com/9o9as.jpg
When you are at the peak of your jump, use your Goblin Glider.
https://i.imgur.com/2wQMh.jpg
You will land on the rock behind the first rock.
https://i.imgur.com/fhEmv.jpg
Now you will jump from this point with your Goblin Glider to the huge rock behind mage tower.
https://i.imgur.com/QSs0Z.jpg
https://i.imgur.com/DhQyA.jpg
When you have climbed ontop of the huge rock, you will jump from this point to the mage tower using any slowfall or such.
https://i.imgur.com/gqczE.jpg
https://i.imgur.com/wm9Pd.jpg
Congratulations on getting ontop of Mage Tower.
https://i.imgur.com/TfhkP.jpg
You are unkillable and able to capture the tower while up there.
Video of us doing the bug.