Originally Posted by KazikluBey
The bug isn't that you're unable to kill the Githyanki captain, but that a certain script that interrupts the action doesn't fire. I had that bug last time I played through BG2, and it took a couple of reloads before it played out correctly.

Interesting I assumed it was another case of unkillable enemies introduced by Unfinished Business since the trolls were confirmed as such.