The fine lad that plays Agent Jameson Locke in Halo 5: Guardians and in Halo: Nightfall has spilled the beans in an interview with Official Xbox Magazine.
Apparently, Agent Locke is a playable character in the game - hence the box art showing Locke above Master Chief.
Hopefully it's good like the Arbiter and it doesn't suck.
(Potentially minor spoilers within.)
http://www.xboxachievements.com/news...medium=twitter
SUPER EDIT:
HOLD THE PHONE. According to a Microsoft statement and after looking at the interview with OXM more, it looks like MC won't be the primary playable character - Agent Locke will.
http://www.xboxachievements.com/news...medium=twitter
http://www.eurogamer.net/articles/20...lo-5-guardians
Master Chief will play an "integral part to the story and as a playable character", and Michael Colter, Agent Locke himself, said "you're basically going to be playing a game with me as the primary character".
NO.
NO.
BAD, 343! BAD!
SPECULATION TIME:
This makes me believe that the first half of the game is going to be us playing as Locke tracking down the Chief. There'd be a lot of chatter as you make your progress.
Then, Chief and Locke either join forces or butt heads and save the galaxy.
FC Media Links