So, the Halo story I have in mind is a story where a Sangheli warrior that is an orphan and is raised by a San Shyluum. While growing up and being mentored, this male Sangheli warrior believes in what the Covenant is doing is the right thing. Until one day, when he fights in an campaign as an Elitie minor on a planet from RVB named Chorus. He fights well throughout the campaign, cutting through the Federation and the Rebels. Until he encounters a demon, then after an intense fight, the warrior gets the upper hand by slashing through its glass helmet with its energy dagger. When he's about to make the final kill, he resists cause he truly sees who's behind that glass mirror helmet and starts to question whether he's doing the right thing or not due to the fear he sees in the human Spartan eyes.
After this, he gets arrested and is banished to a prison/forgery encampment, where he makes some friends and is forced to build destructive weapons for the Covenant's treacherous war. Until one day when a squad of humans find the place and try to take what they can to fight against the Covenant, but also find any evidence that could help them to win the war. So, the Sangheli warrior and his friends, which is a Serian like a Sangheli and Kid-Yard fight against the humans and destroy the facility.
Due to his actions, the Prophets allowed him and his friends to come into the Covenant, but they must served under a Shipmaster. WHo's secretly a hunter for the Prophets when it comes to loose ends.
This is the idea for the story so far, it might change during the process. Also the events in the story will take place before MCC, where it has the games from Halo: Reach to Halo 3. Cause after that, I'll envolved the aftermath of the war but in a different way then it originally goes for the Arbiter and Sanghelios.