Ghidorah, or Monster X as he is commonly known as, made his debut into the Monsterverse in 2019's
Godzilla: King of the Monsters. The three-headed dragon is a staple of the original Toho films, and most well-known for acting as Godzilla's archnemesis. Throughout his many iterations, Ghidorah has always hailed from a far away world, coming to Earth to claim it has his own, stopped only by Godzilla himself.