Niemain is a mage who is found upstairs in the Sorcerous Sundries shop. When the player goes upstairs in the Sorcerous Sundries, they will find Nieman practicing a spell, and he will hail you on sight. He will warn you, quite rudely and even beligerently, and if you don't apologize and leave immediately he, along with three other mages (Oulam, Wheber Ott and William Garst) will attack unless Xzar and/or Montaron are in the party, in which case he will mention that Xzar has sent him reports about you and that you should investigate the Iron Throne headquarters in the city. If Xzar is alive, you can ask him about Niemain and his group, and he will reveal that he is a Zhentarim and Xzar's superior.