The Imperial Library

After the fourth piece, Ria Silmane met the champion in his dream:

"You have recovered the fourth piece! I honor your bravery. Listen closely now my friend, for Tharn has begun in earnest to look for you. Do not fear, he does not know your true identity, but he can sense the Staff's power. With four of the eight pieces, you stand out like a lantern at night. I urge you to caution. The fifth piece of the Staff lies in an ancient stronghold of sorcery called the Crystal Tower. It was said that the southern tip of the Dragon's Teeth, which stretches from the ice covered mounts of High Rock to the wooded forests of Valenwood, could be seen on the horizon from the top parapet of the Tower. This would lead me to believe it is not far south of the majestic mountain range. You must find the Tower and gain access to recover the fifth piece of the Staff of Chaos..."

The place is located in Summurset Isle province. Again to get the place of the Crystal Tower, the Eternal Champion had to consult Mages Guild of Lillandril. A few nights before, priests of the Mad God attacked the Guild. They stole a number of the guild treasured artifacts. Among these was a small diamond. It is said that the light from the gem will allow the viewer to see the true location of the Crystal Tower on a specially prepared map. After the problem with the priests in Mad God Temple, the champion delivered the gem and rewarded with the true location of the Crystal Tower.

Exiting the tower, the Eternal Champion was greeted by Jagar Tharn again:

"I have underestimated you, that is clear. You have not only defeated the useless creatures I have sent against you, but managed to survive the Crystal Tower, a feat that in and of itself could be legend. It is sad that I am forced to destroy you. Prepare, for my minions arrive..."

Yeah, Tharn is really underestimated the Eternal Champion, he kept sending weak creatures.