You find a patch of edible funghi. They taste well and all, no ill effects. UNLESS you consume some beverage, even 3 (three) days after eating it. Then you become really sick with pains, vomiting, all the fancy stuff. As a gift or good meal, it could be a cruel joke or to make sure the heroes spend their time focused on the mission. And the fine soup you had in the inn yesterday could have some in.
(Inspired through a real-world fungus. Was really used to cure alcoholism.)
To become a warrior in a tribe. -no food, drink, or sleep for 4 days and nights. -change into special clothes and painted enter hut -slices of skin carved from their chest and shoulders -wooden skewers through the bleeding flesh behind the chest muscles -stout thongs, secured to rafters were tied to skewers -hoisted from floor by these and weights were attached to their feet -twirled around till fell unconscious -when recovered from this, given a hatchet to cut off their little finger -ropes then tied to wrists and force to run in circle like a horse until he passed out -if survive all this he can return to his family in honor knowing he is now a warrior.