After almost being killed by Godzilla, Gigan retreated to his home planet. However, he carried back some of Godzilla's DNA to the planet. The DNA was exposed to the atmosphere, causing the planet to explode (which killed Gigan). The explosion and DNA combined and created Monstra, the evil kaiju. He tracked down Godzilla and headed for Earth. The King of Monsters rose from his trench and made Monstra retreat, saving the Earth.
Monstra can achieve flight at mach 4 and shoot a sun beam from each of his claws. The sun beam is a ray made of the same gasses as the sun is made of, and explodes on touch. He can also breathe in air, water, and outer space.
He is 80 meters tall, has the head of a sperm whale (except silver) with white eyes on top of his head, and twelve razor-sharp teeth on his bottom jaw only. His body is dark blue, but the flaps of his wings are light blue. His arms are thin but have sharp claws and his legs have three toes.