Duel Monster Spirits, Duel Spirits, or what are now known as Duel Monsters is the name given to the magical, spiritual, and otherworldly creatures who have the capability to be summoned by a duelist. Ancient legends and carvings of Duel Monsters inspired Maximillion Pegasus to create the popular card game of the same name. They live primarily in the Duel Monsters Spirit World, although their relationships with humans and Earth are sometimes unclear, and differ within the different Yu-Gi-Oh! series. It is unknown if every Duel Monsters card created within the Yu-Gi-Oh! universe has a Duel Spirit counterpart that can be summoned accordingly.