So before you get to the rafters, from the room between he and Glut, there is a catwalk at the same height as the rafters (accessibly from the second story ladder in Glut's chamber). You will know you are in the right place if on either side of it there are chests, one across a divide the other around a corner. From that cat walk you can just target the wandering goblins in front of the throne. So, don't hide, take pot shots without killing them until one spots you. He will immediately run out hunt you down but it takes him four turns or so to reach you.

Once you have acquired his aggro, concentrate fire on him and anyone within visibility so that after each attack you can hide. I took him out with cantrips and crossbows. Sneak attack helps a lot because you will always have advantage. He should never even get close enough to lay eyes on you

Last edited by DistantStranger; 03/11/20 03:57 AM.