All TOTSC does is add a few new areas: Durlag's Tower, Ulgoth's Beard, Werewolf Island, and another (nameless) island. These areas are accessible anytime throughout the game. To get to Ulgoth's Beard, I
think all you need to do is travel north far enough until the area on your map turns blue. But I'm not really sure on this. I usually head for Ulgoth's Beard at around 6th level - Durlag's Tower I tackle when I'm 7th. These areas are pretty tough and certainly not to be underestimated. But they are treasure troves of experience - one can gain roughly another 40,000xp (in a party of six) by adventuring through these areas. Good luck
