Congratulations, that boss was extremely difficult, I just ended up summoning a load of monsters to hold him off while I killed all teh disciples, then beat on him. The annoying thing was that death stare that turned your party members into ghasts. It was perma death too
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Oh, and yes, you're nearing the end of BG1... But theres still BG2 and ToB to go yet, which continue the same story, so in reality, you're barely half way through
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