Halo 5: the agent Locke will be a playable character, Nightfall poster and trailer
Halo: Nightfall tell the story of Jameson agent Locke, in its evolution from a simple ONI agent to become one Spartan. Frank O Connor of 343 explained that Locke's story will be that of "origins of a superhero", and will be much more integrated with Halo 5: Guardians than it was Forward Unto Dawn with Halo 4.
The fact that it will be a playable character, and that Microsoft and 343 are dedicating so much of the spotlight, suggesting: that we are preparing to introduce a more human character, with a face and a well-known background, intended to be Master Chief in the hearts of the fans of the series? To find out if it is really so we'll have to wait for before the TV series, arriving in November on Xbox One, and then exit the game at the end of 2015.
Meanwhile we show a first trailer of Halo: Nightfall, showing scenes of the series, an image of "poster" of the game shown at the San Diego event, worthy of a true sci-fi blockbuster, and new shots from the set. Good vision!