Take the oath: “I solemnly swear that I am up to no good.” There… now you can order this Harry Potter and the Prisoner of Azkaban I Solemnly Swear 20 oz. Heat-Reveal Mug featuring the Marauder’s Map. When it’s cold, it shows the oath on one side and the map on the other. When you add a hot liquid, little footprints are revealed! It’s magic! Hand wash only. Not dishwasher safe. Do not microwave.