I tell everyone except Theo. Just kidding. Actually, I tell everyone, and I use the Chromatic Orb as proof ("Snakes can't cast Chromatic Orb.").
Save v. spells = 14, which I believe is a success, but I'm not positive.
I attempt to Find Hidden or whatever, BR 15 would succeed in Wisdom but nothing else. D6 = 4.
"Don't worry, we don't want to kill you. We are just some simple adventurers trying to do a simple chore to pass the time. In fact, one of our members is an illusionist. Perhaps we could talk and see if we can team up? We're not a violent bunch." Cha check 7.