Ymir

The Ymir is a non-sapient, reptilian humanoid native to planet Venus. Virtually nothing is known about the Ymir in its natural habitat, except that it feeds on sulfur and is somehow able to survive in the harsh environment of its home-world.

History
An Ymir egg was found by Human scientists during an expedition to explore Venus and its mineral resources. The egg was brought to Earth to be studied, but unfortunately, the spaceship crashed on Sicily. When the Ymir emerged from its egg, it began to grow more and more due to the oxygen-rich atmosphere of Earth. The huge beast started causing chaos and destruction as it searched for sulfur to eat. The alien was eventually killed by Human authorities.