This is just what I think. Somehow Master Chief and this new Spartan are on the same team. There is a voice speaking to 8 o clock talking about how Chief is the seed of the future but were sown in his past. Meaning he was meant to be an instrument of War. I think somewhere in the story ,at a certain time, 8 o clock arrives to help Chief on the mission of the story which has not been laid out yet. I think 8 o clock is a spartan that was captured by the Forerunners, because his suit looks very updated. When he was captured the Forerunners started to plot against mankind and the Covenant. 8 o clock was used to fight against his own brothers ,so to say, or else he would be killed. After he received his Armor update he turned against the Forerunners. When he ran away he had to wait for Chief to be revived from his pod, in Halo 5, that way they could fight together against the Forerunners. In Halo 5 the Covenant will still be on the Forerunners side. They are only being used as suicide partners though to hide the truth of the Forerunners purpose. In Halo 6 the Arbiter will arrive and Arbiter, 8 o clock, and Master Chief will rise to battle the Forerunners.
His name is Agent Locke not 8 o’clock. And the voice speaking to, reciting John-117’s history is Thel, The Arbiter himself.
And we see an ONI badge on his armor, meaning Locke is an agent of ONI. If you want to know Locke’s origins, check out HALO: NIGHTFALL when it premieres on November 11th. You’ll need a One and the Master Chief Collection, but that series will detail how Locke becomes the man we find in GUARDIANS.