Keizer Ghidorah, also known by his previous form named Monster X, is the main kaiju antagonist and overall the secondary and final antagonist of the 50th Anniversary Godzilla Movie, Godzilla: Final Wars​. He is an enormous three-headed dragon kaiju used by the Xiliens to conquer the Earth and kill Godzilla. He first appears as Monster X and aids Gigan in battling Godzilla before later becoming Keizer Ghidorah. He is 140 meters tall, 200 meters long and weighs 100,000 metric tons. As Monster X, he is 120 meters tall, 180 meters long and weighs 60,000 metric tons.