While Chief boasts top-billing in Halo 5: Guardians of Ga'Hoole, Agent Locke (pictured above) will have a "key role" in the proceedings, 343 studio boss Bonnie Ross told Eurogamer. Apparently Ridley Scott's digital series Halo Nightfall, which will launch with the Master Chief Collection (11/11), will tell Locke's origin story, "so when you end up with Halo 5: Guardians you have an idea of the background of this new character."
Seems like throwing backstory important to character development away in alternative media, but maybe these productions are all more connected than we give credit. I mean, people actually read the Halo novels. And apparently Halo 5 is meant to align strongly with Steven Spielberg's Halo TV show as well. It's a whole transmedia thing.
Chief will still be the star of Scott's series, however, as well as Halo 5. "He is human, he's always been human, but at the end of Halo 4 he really is reflecting on who he is and why he exists. That was very deliberate because the story we want to tell on Xbox One really is an important part and the main part of his hero's journey. It's more about what he's searching for versus what the UNSC is asking him to do. [Halo 5 is] a continuation of Master Chief's story."
You'll be able to play Halo 5 in its newly built engine during the multiplayer beta if you buy the Chief Collection. It begins December 27.
343's master plan for Halo 5: Guardians [Eurogamer]