The site previously reported that Braniac would be the film's villain. The site now adds that Braniac is after the Kryptonian codex from Man of Steel, and that the codex will end up in the hands of Supergirl.
This version of Supergirl was first introduced in the Man of Steel prequel comic as a new member of the Kryptonian Explorers Guild, and organization tasked with seeking out suitable planets for terraforming and later colonization by Kryptonians. The report suggests that the plan has always been for the Man of Steel sequel to focus as much as Kara Zor-El as on her more famous cousin, and that her inclusion is what got George Miller's attention in the first place.
The reports also states that Braniac will use what Kryptonian data he already possesses to create Bizarro to aid in his battle against the last scions of the House of El.
This is all unconfirmed, of course, as future DCEU projects are still shrouded in secrecy.
Check out when the future DCEU movies and other movies are coming out in ComicBook.com's Movie Release Schedule.