Now that you've gathered all the items I'll need to break Kael'thas's curse, one thing remains to be done. When Kael'thas sealed the tower, he placed an arcane golem, known as Ar'kelos, at the bottom of the tower.
You must defeat Ar'kelos in order allow me to work magic within the tower again.
When you enter the Violet Tower, the curse will begin to affect you.
Once you have defeated Ar'kelos, ascend the tower and assist me in making preparations for the ritual.
You have done well, <name>. Destroying the dampening field will make it much easier for me to prepare the magic that will lift the tower's curse at last.
Shortly after the quest is turned in, Vargoth will begin a spell which is planned to release him from the tower.
I can't thank you enough for your help, <name>. At long last, I will be free of this tower and Kael's damnable magic!
Vargoth begins to cast various effects, such as summoning three blue levitating rocks (Stone of Glacius perhaps?). Eventually, he is knocked back as the magic suddenly malfunction.
No! How could the ritual fail?
The curse remains intact. We'll have to find another way.