Listen to me, you are never to return here. Your are to stay away and tell no humans about this place. Or I will track you down, and suck every ounce of blood from you body, until you look like a deflated whoopee cushion! — Hotel Transylvania

There’s nothing wrong with being completely forthright about your intentions.  If they don’t have to wonder about what you’re going to do, then you can move onto things that are important.