X the Unknown

X the Unknown was a sentient creature that arose in the early, molten years of Earth from a combination of primal mud and radiation. As the planet cooled, X and its fellow creatures moved deeper into the planet, only nearing the surface again on rare occasions. Following humanity's experimentation with radiation, the creature that became known as X decided to stay near the surface to feed. Emerging in Scotland, it terrorized several cities before it was destroyed by waves of radiation-negating energy.