Mizushi(New Age of Monsters)

Mizushi is a giant octopus Kaiju that laid dormant for centuries and the main antagonist of the Godzilla: New Age of Monsters TV special, Godzilla: It came from beneath Tokyo.

Origin
For centuries, the monster has laid dormant beneath Tokyo until man had disturbed Mizushi from his slumber. Because of this, Mizushi goes on a rampage through the world's ocean, attacking ships and whales.

History
The Gammas had a hard time battling the massive cephalopod as did Giant Robot and Zone Fighter. During the first battle, Toby get amnesia and Starman gets a leg injury. Mizushi then attacks Tokyo as the Gammas went to save the city and the people.