‘Legends of Tomorrow,’ ‘Arrow,’’ Supergirl’ & ‘The Flash’ Crossover Trailer: What We Know So Far

The trailer for "The Flash," "Supergirl," "Arrow" and "Legends of Tomorrow" crossover episode contained enough spoilers to excite fans ahead of its release. The preview, titled "Heroes v Aliens: The Dominators," sees the team fighting against their most powerful nemesis yet.

The CW has released a 2-minute trailer for the upcoming crossover episode, titled "Invasion." The trailer opens with The Flash stumbling upon the crashed alien spaceship. He then warns his team about the aliens.

Naturally, the first person Barry Allen asks for help is Kara Danvers. She has more experience with extraterrestrials than Team Arrow or any members of the Legends of Tomorrow. The trailer shows a scene from "Supergirl," where Barry consults the team about the aliens. He learns that they are called the Dominators.

Of course, Supergirl and The Flash cannot handle the hordes of Dominators on their own, so they ask the other superheroes for help. "Heroes V Aliens: The Dominators" shows Barry telling Team Arrow about the alien invasion. He also asks the Legends for help. The trailer ends with the superheroes assembled for an epic battle against the Dominators.

Likewise, the trailer revealed other spoilers outside of the alien invasion plot in the "Arrow," "Supergirl," "Legends of Tomorrow," and "The Flash" crossover. The episode also sees the heroes battle each other.

The scene at the 1:37 mark in the video below show Sara Lance aka White Canary fight a hooded man. Is she fighting Green Arrow? Another scene, at the 1:40 mark, shows The Flash up against someone who looks like Vixen. Supergirl then slaps hands with him after he defeats the woman.

Likewise, the trailer shows Diggle pin a man to the ground. This man shows a resemblance to Leonard Snart aka Captain Cold. Will viewers see the heroes battle each other in the crossover episode? Who wins the battle, the Dominators or the heroes? Find out when the "Invasion" episode kicks off with "Supergirl," followed by "The Flash" and "Arrow" and ends with "Legends of Tomorrow" Season 2 Episode 7.