Monster X is a powerful and enigmatic kaiju that appears in the 2004 film 'Godzilla: Final Wars' (part of the Gojira franchise). As an extraterrestrial monster, Monster X serves as one of Godzilla's most formidable adversaries, later transforming into the even more powerful Kaiser Ghidorah. With a skeletal, humanoid appearance and immense strength, Monster X challenges Godzilla in a climactic battle, showcasing his role as a major antagonist and a symbol of alien threats in the series.