An installment in the long-running Sonic the Hedgehog series, Sonic Unleashed opens with the hero's archenemy, Doctor Eggman, springing an elaborate trap. Using a powerful laser, Eggman shatters the very planet into pieces and awakens Dark Gaia, an ancient evil that has slumbered at the world's core since time immemorial. The catastrophe leaves its mark on Sonic himself, afflicting him with a strange new condition that transforms him into a hulking, werewolf-like Werehog whenever night falls. Determined to undo the damage and stop Eggman's scheme, Sonic sets out to restore the broken world piece by piece. His journey carries him across a series of continents inspired by real-world locales, where by day he races through levels at his trademark blistering speed, and by night he battles the creatures spawned by Dark Gaia using the Werehog's raw strength. Torn between his two forms, Sonic must piece the planet back together before the awakened darkness consumes it entirely.