When the TV show based on Halo was first announced, Kyle Killen was attached as its showrunner (Killen previously worked on one-series wonders Lone Star, Awake, and Mind Games). Killen apparently stepped down and Steven Kane (whose production credits include American Dad! and The Last Ship) took over as showrunner. According to Variety, even if Halo is picked up for a second season, Kane won't be sticking around. He'll be leaving Budapest, where Halo is being filmed, to return home to the United States.
While initially announced as a Showtime project, the Halo series will debut on Paramount+. Pablo Schreiber from The Wire and Orange is the New Black has been cast as Master Chief, and Jen Taylor, who voiced Cortana in the games, will reprise her role. Natascha McElhone will play Dr. Catherine Halsey, with Shabana Azmi as Admiral Margaret Parangosky and Bokeem Woodbine as a privateer and old friend of Master Chief's named Soren-006.
As for what it's about, the Halo TV show will be a new story rather than a direct adaptation of any of the games or novels, although back in 2018 Showtime's president of programming Gary Levine described it as being "incredibly respectful of the canon". Halo is currently scheduled to release early in 2022 on Paramount+.