The game sets the stage for a new story in which Master Chief returns to confront his destiny and face an ancient awakened evil that threatens all life in the universe. The main campaign also heavily explores the relationship between Master Chief and his AI companion, Cortana. Cortana is nearing the end of her life, before devolving into a state called Rampancy in which an AI begins to think itself to death. The campaign features both first-person shooter and driving elements, and can be played either single player or co-cooperatively (either over Xbox Live or split-screen). It features new weapons and an entirely new class of enemy characters called Prometheans.
Spartan Ops is an episodic cooperative campaign which contains ten episodes, in which the player plays as their Spartan IV character. Spartan Ops is set 6 months after the end of the campaign and continues the adventures of the Infinity's Crew. Each episode is released weekly and contains a new cinematic along with 5 new missions to complete. These missions can be completed solo, but are designed to be played cooperatively, again over Xbox Live or split-screen.