Bring the Sealed Description of Thredd's Visitor to Baros Alexston in Stormwind.
During the first years of Thredd's imprisonment, he never had any visitors. I figured that he was no longer of use to the Brotherhood, so they abandoned him.
Anyway, a few months ago, that all changed; he started to get regular visits... once, maybe twice a week. It was a strange man--the quiet type. I had my suspicions, but all his papers checked out.
His documents claimed his name was Maelik; here's his description. I don't think he'll be coming to visit Thredd anymore.