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.”
Actually a real-world fungus, just heard about it. A fungus that tastes well and all, no ill effects. UNLESS you consume some beverage, even 3 (three) days after eating it. Then you become really sick, pains, vomiting, all the fancy stuff. Was really used to cure alcoholism. May be a joke or to make sure the heroes spend their time focused on the mission.