The merchant grinned “Dear sir, I noticed you had your eye on that charm. Might I interest you in a little bit of its history? Of course I would. I will have you know, that charm has seen its way through many an adventure, and saved the lives of many of the adventurers therein. Legend tells that it was crafted centuries ago by Yurid Norcral, the greated Dwarven runesmith to ever live. Later it was said to have been enchanted by ancient Elven magics which have since been lost to the ages. Quite a rare find.”
If you want to add a "supernatural" touch to your campaign, define the rules of magic and the universe. Make your players comfortable with those rules. Then your new supernatural creatures must then break those rules.