Let's say you are cornered by your worst enemy. They will kill you, but being an oddball enemy, they'll give you one request first. (And the request can't be "Don't kill me." They're on to that one.) I have a solution for you. Ask them to show you how DeLand's Paradox works. That will keep them busy for years while you live a happy and productive life. It will, however, make them justified when they finally get around to killing you.

A graphically obvious version of DeLand's Paradox is Curry's Triangle. It's a triangle sketched out on a backing of graph paper that, when rearranged on the same paper into the seemingly same shape, will suddenly be missing a square in its center. Careful observation will show you that the hypotenuses of the first and second triangles are slightly curved. One is curved up and one curved down, giving them slightly different areas, and accounting for the missing square. It's a good trick.

So of course the puzzle-makers changed it into a torture device. Theodore DeLand was a designer and amateur magician, and he did his own version of the triangle. He sketched out fifteen playing cards (maybe); the image he sketched was meant to be cut out and rearranged into an image with the overall same dimensions, but with slightly juggled pieces. In this new image, there were sixteen playing cards.