An official synopsis for Batman v Superman: Dawn of Justice has surfaced online and it teases a key detail, apart from the two superheroes going into battle with each other.

Check out the synopsis below. (via Collider)

Fearing the actions of a god-like super hero left unchecked, Gotham City's own formidable, forceful vigilante takes on Metropolis's most revered, modern-day saviour, while the world wrestles with what sort of hero it really needs. And with Batman and Superman at war with one another, a new threat quickly arises, putting mankind in greater danger than it's ever known before.

Who or what is this "new threat" that "quickly arises"? By now, fans who are eagerly waiting for the film to release next year will know that Lex Luthor (played by Jesse Eisenberg) might be the primary villain in the film. However, rumours of another Superman villain -- Doomsday (in complete CGI glory) -- being in the film, have been circulating for some time now.

Superman vs Doomsday fan art
Superman vs Doomsday fan art

Reportedly, the makers want to keep Doomsday's role in the film a secret. The deadly, monstrous villain can definitely pose a major threat to mankind.

It remains to be seen what this new threat is and whether or not it is big enough to take on both Batman and Superman. With The Justice League films already announced by Warner Bros, there's a strong chance that the Batman v Superman storyline, with regards to its villain(s) will spill over to the subsequent films.

Batman v Superman: Dawn of Justice is slated to release on 25 March 2016.