For the nearly two centuries since this Etruscan oil lamp was found near the city of Cortona, Italy, it has confounded scholars. It was unearthed in a ditch, so its original context is unknown. And its combination of imagery is unique in the ancient Mediterranean world, leaving nothing to compare it with that might hint at how it was used. On the bottom of the lamp, at the center, is an image of a fearsome Gorgon surrounded by snakes. This Gorgon is encircled by a frieze of animals, including dolphins, in combat. In the next ring, crouching male demigods known...