Just finished Stonekeep for the 2nd time. Great game. Thanks to GoG and others who post on this forum.
SPOILER:
I have generally had PITA problems with the Invincible Spinner in Kull Khumm's Tower. I first opened the porticullis with the pushbutton on the wall to the left of the gate. This time, before I approached him/it, I used the 99 point runestaff to set up a home teleport blue circle at the intersection between the porticullis and the Spinner. I then used the appropriate Orb to give myself "Quickness." I then approached the Spinner and then backed through the porticullis and into the four-by-four room where he usually kills me. As soon as he caught up with me, I activated the Teleport spell to the blue teleport home circle. By the time he figured out where I had gone, I had pushed the gate access closure button and locked him behind the porticullis.