Halo 3 - the complete story

Level eight:

The story: We've been here before... Chief heads to High Charity to confront the mysterious Flood organism, Gravemind. With Cortana's life in danger he must rescue her and secure The Key, in order to activate the rings once and for all, wiping out the Flood. Here Master Chief will take on the role of Orpheus (explained later).

The evidence: Now we saw High Charity a fair bit throughout Halo 2's storyline, and ended the game with Cortana trapped within the clutches of Gravemind, the menacing Flood hive mind that had taken control of the Covenant city. We see a transmission from Cortana, clearly distressed and in dire need of help. Can you save her? We're saying: perhaps not.

The gameplay: Expect it to be dark and gloomy. High Charity is severely lacking in power and, under the might of Gravemind, is falling apart. Here you'll be relying on your torch as you make your way through the Covenant city battling the Flood and whatever tricks ol' Gravy can throw at you. You'll not be alone though, as the E3 trailer shows us the Chief, Arbiter, 343 Guilty Spark and an unknown Elite all make it aboard.