Just give him a mist knack/quickenings. Make sure that your main guy goes straight for Bergan, and the others can mess up the rooks.
That's what I had been doing...
I just realized the full potential of Quickenings, and I finally figured out how to get him. Success!
"Whatever you do, work at it with all your heart, as working for the Lord, not for men, since you know that you will receive an inheritance from the Lord as a reward. It is the Lord Christ you are serving." --Colossians 3:23-24