Hmm...It's a powerful reflection ring, but Darahil probably would have tried to find a protected spot for it. There's no knowing where it came from, so it could have some extra benefit for Vile. By this point, Darahil probably would have analysed it to the best of his ability and found nothing outwardly suspect, but he wouldn't be confident that it's absolutely clear of risk to use. "A Daedra did it" and so on. If Meesei looked at it, she would probably come to the same conclusion.
I'll get a post up in a bit.