Halo: After Requiem

After Requiem Master Chief was without an AI, but that doesn't mean that ONI couldn't use him. He's been assigned to Infinity to help train the other Spartans in preparation for their next venture into deep space, to a mysterious phenomena dubbed the "wormhole nexus". Not to mention a mysterious group of UNSC personnel rescued after being adrift in space for two months. What is the secret behind the wormhole nexus and the rescued UNSC personnel? What other massive forerunner weapon will the humans discover this time?
Notes: This is headcannon of sorts after the events of Halo 4 main campaign and Season 1 of Spartan Ops. Character may have repeated names with some other stories but that doesn't mean they're the same person, if they are or somehow related then I will be sure to let you know.