The First Generation Godzilla (初代ゴジラ Shodai Gojira) is a kaiju that first appeared in the 1954 film, Godzilla. The original Godzilla is a prehistoric amphibious sea creature that was disturbed and burned when an American hydrogen bomb test conducted in the Pacific Ocean destroyed his habitat and drew him to the surface. Godzilla took out his rage upon humanity, destroying any ships in his vicinity and eventually laying waste to Odo Island and the city of Tokyo. Daisuke Serizawa eventually used his invention, the Oxygen Destroyer, to kill Godzilla, while taking his own life to ensure the weapon could never be used again. Typically, in the various continuities of the Godzilla franchise, a second Godzilla appeared sometime after this Godzilla's death. Despite only being the focus of one film, the 1954 Godzilla has been referenced to some degree in several entries in the series since. In the film Godzilla Against Mechagodzilla, the remains of this Godzilla were salvaged by the Japanese government and converted into a bio-robot dubbed Kiryu in order to battle against a second Godzilla. The original Godzilla's spirit remained attached to the machine, and at some points even took control of Kiryu and rebelled against its human masters.