As soon as you get to the prison, use stealth. As long as the guys are not hostile and you have a good score in stealth, you should go invisible. The mage will try to counter this with true sight, but you should backstab him quickly.
Also, try to summon a creature to help you out. A berserk warrior or Kitthix come to mind. The fighters should be easy. If you are finding it tough, run away and stealth again. Then backstab. This strategy served me well.
Also, you could buy a potion of magic resistance from Roger the Fence in the temple sewers and chug it before you follow the troupe. Consider other potions as well, like the potion of speed to keep up with the halfling.
[ 09-23-2002, 01:54 AM: Message edited by: pcgiant ]