This quest is the last step in a quest chain in Netherstorm that begins with  . Commander Sarannis drops the quest item in normal and heroic modes.
In order to break this curse once and for all, you must enter Tempest Keep and claim .
Did you obtain the keystone?
<The archmage's eyes light up when you hand him the stone.>
Amazing! From what little I've see of the fate of Farahlon, I'm not certain I want to go outside, but it's much better than being trapped here for the rest of my days.