[Kormar the Wanderer]

Just a tip.

This is one of the fights where web is most effective. Move your magic users to just outside his line of sight so he hasn't appeared yet and fire off a few webs as far away as you can without revealing him. When he does appear odds are pretty good that he'll fail his save against at least one. You can then pound on him from a distance with magical spells and magical arrows. Also, I believe that a dispel magic will destroy his blade, making him far easier to deal with if he does manage to get in close...