When Halo 5: Guardians was announced, fans of the series rejoiced at the return of the critically acclaimed franchise. An image was unveiled, stirring much excitement, but also some questions. The most important being: Who is that?

A Spartan 4, the latest version of the Spartan Program in the series introduced in Halo 4, was shown reflecting Master Chief, the main protagonist of the franchise. When the trailer for Halo: The Master Chief collection was shown at E3, this mystery character showed up again. While everyone loves a good team-up in video games, this character had never been seen, heard, or even mentioned before in the games or books. He is clearly involved heavily in the story of Halo 5. Apparently, who this character is, is quite important.

In an interview with Eurogamer, Bonnie Ross, studio head at 343 Industries, dropped some details about who the character is, what he means to the story, and where we can find out more. The Spartan’s name is Agent Locke, and he will be the focus of the upcoming Ridley Scott produced Halo: Nightfall. The series will explore his origin story so that, as Ross puts it, “when you end up with Halo 5: Guardians you have an idea of the background of this new character”. She also says that Locke plays a “key role”, and that an important part of Halo 5 will be about the dynamic between him and Master Chief.

Ross also said that fans shouldn’t worry that Master Chief won’t be the focus of the story, which deals with a much more personal look at the stoic hero. “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,” Ross explained. “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: Guardians is a continuation of Master Chief’s story.”

The first episode of Halo: Nightfall is expected to be released November 11th along with Halo: The Master Chief Collection on Xbox One, a compilation which includes remastered versions of Halo: Combat Evolved, Halo 2, Halo 3, and Halo 4. Halo 5 is expected to be coming to the Xbox One in 2015.