At the same time as confirming the beta for Halo 5: Guardians and the Halo 1-4 remasters coming in The Master Chief Collection, Microsoft's stage at E3 also saw the announcement of Halo: Nightfall, a live-action digital series that'll be included in the aforementioned Master Chief Collection.
It's being created as part of a collaboration between Xbox Entertainment Studios, executive producer Ridley Scott and Scott Free TV President David Zucker, and will be directed by Sergio Mimica-Gezzan ("Battlestar Galactica" and "Heroes").
It was also confirmed that the series would be introducing "a pivotal new character" from Halo 5: Guardians.