The Dark Mark is a symbol associated with the dark wizard Lord Voldemort and his followers, known as the Death Eaters, in the Harry Potter series by J.K. Rowling. It resembles a skull with a snake protruding from its mouth and is used to signify the presence of the Death Eaters. When conjured, it appears in the sky as a signal of terror and a call to arms for Voldemort's followers. The Dark Mark can be summoned by the Death Eaters using a spell, and it serves as a mark of loyalty to Voldemort. It is also branded on the forearms of the Death Eaters, allowing them to identify each other. The symbol represents fear and the dark influence of Voldemort throughout the wizarding world.