[andrewas]

If you dont mind cheesing the battle - wait for him to fail his resistance on his own stun attack, and then put an otilukes resilient sphere on him. fist atacks will get though the sphere (one of my fave BG1 exploits), but hes immune to non magical weapons.so use the time to smash his followers, and then the sphere will prevent him casting the ghast portion of his gaze attack (its implemented as gaze and the ghast spell from aec'letec, the later one being automatic,instant and un-interuptable). when it wears off you have 2 or 3 tanks ready to beat him up. no ghast problems, no demon problems, no problems.