It seems like the line between friend and foe with Batman and Superman could be thin after the events of the team-up film coming up. But could the Caped Crusader really keep the weakness of Superman to use just in case?

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According to a source with Fanboys Anonymous last week, it seems like Batman could be in possession of some Kryptonite by the end of Batman v. Superman to either help or use against Superman during Justice League.

"The source says that Luthor, before and during the course of the film, collects pieces of the destroyed World Engine in an attempt to synthesize Kryptonite," the site said.

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"At the end, Batman apparently breaks into Lexcorp to steal said kryptonite-whether in defense of Superman or with intent to use it against him, we don't know."

This is an interesting set-up for Justice League, which hypothetically could have all the DC heroes working together in a major Avengers-like team-up to fight a common enemy. But clearly, Batman doesn't trust Superman enough and could be keeping the hero's weakness with him just in case he starts to get to be too much.

Fanboys Anonymous also added that this news could mean that Batman v. Superman is more directly linked with the Justice League franchise rather than the Man of Steel franchise. With a sequel to Man of Steel not coming until around 2018, it seems like the singular story for Superman will just have to wait.

Justice League is set to open in theaters in 2017.