I can hardly say that I blame you. From what I recall of confrontations with Grima, there were very few ways to defeat him, one of them was to try to seal him away... which was one of the more difficult... because how would one seal away such a being? Another was gifted to us by the divine dragon Naga, a hope against the impossible, a blade that couldn't actually kill him, but it would put him to sleep for a thousand years. Then of course there was one other possibility... a chance to end him once and for all... yet it is the most impossible, for Grima can only be killed by his own hand, his own power.