Magical cloak that acts as armor. Protection against normal and magical attacks as well as holy spells. Gives creatures who are harmed by light and sunlight immunity. Give wearer the ability to become invisible at night. Sentient and cursed. See full description for details.
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.)