Unleashed is the third Godzilla fighting game, a series that began in 2002 with Godzilla: Destroy All Monsters Melee (Gamecube/Xbox) and continued with Godzilla: Save The Earth (PS2). Once again, the Vortaak aliens are back to try and take over the planet, using huge crystals and Space-Godzilla to destroy major cities.
As with the previous two entries in the series, it's up to Godzilla to fight off the invaders whilst battling other giant monsters. Some creatures are on his side - i.e. Earth Defenders and the Global Defense Force, aka giant robot monsters - but other factions such as Mutants and Aliens are purely in it for the destruction. Although the G.D.F consists of machines created by the government, the mysterious crystals give off energy that can influence them to turn to the Vortaak's side.