Doppelgänger
UNSC’s Spartan-II Project has been a torn in the side of the Covenant specially the Master Chief John 117, and for him the Covenant has found the way to undermine 117’s efficiency. With the help of their Engineers, the Covenant managed to infiltrate a Doppelgänger virus, one that will take over Master Chief’s Cortana and seamlessly replace her. And with that The Covenant will feed Master Chief with data that could lead into his death.