Arrow, Flash, Supergirl & Legends Crossover Has ‘One Unifying Threat’

It has already been revealed that Supergirl will be the focus of the multi-show crossovers, but how that will be done is still a mystery.

That means the Legion of Doom could follow them to Supergirl’s universe, or one of Supergirl’s enemies could join the Legion of Doom.

Where there’s a will, however, there’s a way, and having multiple universes collide is a hallmark of DC comics.