Or do as I did:
Leave him alone until you've done the asylum & underdark part of the story, pay him a visit and chop him up before he can cast his spells. Works like a charm, every time
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The last arrow of Legolas kindled in the air as it flew,
and plunged burning into the heart of a great wolf-chieftain.
All the others fled. -J.R.R. Tolkien, The Lord of the Rings