Well, which witch is it? 
They both sound right, although "witch's coven" seems to imply that only one witch owns the coven (very selfish). I'd use "coven of witches", but it doesn't fit right in the sentence.
They both sound right, although "witch's coven" seems to imply that only one witch owns the coven (very selfish). I'd use "coven of witches", but it doesn't fit right in the sentence.
