The Underdark | Adalon's Lair | Ust Natha | The Beholder Dungeon | The Mind Flayer Dungeon | The Kuo-Toa Dungeon | The Exit Area
KILL A DEMON FOR THE SVIRFNEBLIN
In the Svirfneblin settlement in the top left corner of the Underdark map, speak to Goldander Blackenrock at 15. He will ask you to do the Svirfneblin a favor. In return, he can help you get into the Drow city of Ust Natha.
Apparently the Svirfneblin have been digging a little too deep and released a Balor (major Lord of the Rings reference – the Balrog of Moria!), and now they need you to help them be rid of it. He will direct you to a lady called Adalon, but you will need a Light Gem to enter her lair. The Light Gem is yours, once you have killed the Balor and sealed off the tunnel it came through.
(Of course you can also kill Goldander for the Light Gem but why not take the experience for killing a Demon?)