I knew buying that Horn of Valhalla would pay off. It literally saved Cappen Varra's ass when with only 3 HP left, not a single invisibility potion left and an Otiluke's Sphere disrupted, he managed to place a wall of meat before a Black Ice Knight that had cornered him.
Incidentally it's annoying how difficult it is to disrupt enemy spell casters in
Icewind Dale. I tried a Cloud Kill (which I had memorized specifically to be an enemy spell disruptor) against Kuntik, and despite hurting her every round she had no problems with spell casting. She had some magic effect which I thought was Stoneskin, but evidently not since it was much easier to just rush her and cut her down in one round. So much for subtlety...