Goodmen, Gentles, my Lords, in the best exemplification of the heroic stories you have found the Villain, battled him and his minions, plundered them of their treasure then returned victorious. But Now you discover a greater horror.. Lawyers.. Lawyers...
The modern definition of festival has four parts: 1. a day or time of religious or other celebration, marked by feasting, ceremonies, or other observances: the festival of Christmas; a Roman festival. 2. a periodic commemoration, anniversary, or celebration: an annual strawberry festival. 3. a period or program of festive activities, cultural events, or entertainment: a music festival. 4. gaiety; revelry; merrymaking. In the later eras of the European Rennaissance (early modern) there was an additional meaning; 5. The marking of important events in the life of a princely dynasty, such as marriage, the birth or christening of an heir, a coronation or a funeral, or the traveling to a new country/ state/ city.
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.)