The CW network is gearing up for its most ambitious and most-anticipated crossover yet. Spoilers revealed that the alien Dominator set to terrorize the planet.

In the comics, the Dominators connived with other alien races in an attempt to eliminate the metahumans on Earth. "Arrow" and "Legends of Tomorrow" executive producer Marc Guggenheim told Superhero Insider last month that the Dominators' mission in the crossover is not that different from their main objective in the comics.

"I will say that their goal is very closely related to what was established in the comics, and it does have to do with metahumans," Guggenheim said. "It's very, very faithful to the comics."

Kara (Melissa Benoist) arrives on Earth-1 in the first trailer for this fall's highly anticipated four-way crossover event between "Arrow," "The Flash," "Supergirl" and "Legends of Tomorrow."

In the teaser, Barry (Grant Gustin) introduces Kara to characters from "Arrow" and "Legends of Tomorrow." As seen in the 30-second clip, the Girl of Steel gets to meet Green Arrow (Stephen Amell), White Canary (Caity Lotz), The Atom (Brandon Routh), Heat Wave (Dominic Purcell) and Firestorm (Victor Garber and Franz Drameh), among many others.

The special event kicks off at the close of "Supergirl"'s Nov. 28 episode, which ends with the Girl of Steel "going over to the crossover," executive producer Marc Guggenheim previously clarified. "The story that's being told has a beginning, middle and end: It's a beginning in "The Flash", a middle in "The Arrow", and an end in "Legends of Tomorrow". But "Supergirl "is very much a part of the whole thing."

"The Flash" Season 3 airs on Tuesday at 8 p.m. ET/PT, "The Arrow" Season 5 yesterday, Wednesday at 8 p.m., "Supergirl" Season 2 on Monday at 8 p.m. and "The Legends of Tomorrow" Season 2 Thursday, Oct. 13, at 8 p.m. on The CW.