Many familiar but scary villains are about to crash Barry and Iris' wedding in the upcoming crossover arc titled, Crisis on Earth-X, across The CW shows – The Flash Arrow, Supergirl and Legends Of Tomorrow. And, The CW has released the first look at some of the villains in new promo.

The Crisis On Earth-X event will pit the heroes against their evil doppelgangers from a parallel Earth wherein the Nazis won World War II. The promo gave fans the first look at the evil Oliver Queen in Nazi military uniform alongside several marching Nazi soldiers.

A creepy voice in the voiceover says, "Everyone you care about, everyone you love, they are going to die," as we see fleeting images of Barry and Iris wedding venue being torn into pieces and Cisco, dressed in formal wear standing in a church that seems to be under attack.

Arrow executive producer Wendy Mericle spoke to The Hollywood Reporter about the upcoming crossover and teased a rather emotional episode."The biggest surprise will be the emotional component of the crossover," said EP Mericle and teased a big role for Oliver.

She explained, "I don't think anyone is going to see that coming. It's very much a dark love story. It's the underpinnings of that that will make the Earth-X element a real contrast to that. Oliver [Stephen Amell] has a big role to play in it, and it's bigger and better than any crossover we've done in the past. It's going to be epic."

This year's four-part crossover will air across two nights, beginning on Monday, Nov. 27, with Supergirl and Arrow (on a special night for one week only), and concluding Tuesday, Nov. 28, with The Flash and Legends of Tomorrow. The official plot synopsis reads as follows:

Barry and Iris's wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony. All of the superheroes band together with help from their super friends like Citizen Cold, The Ray, Felicity Smoak, Iris West and Alex Danvers to take on their most formidable villains yet. Earth's mightiest heroes - Green Arrow, Supergirl, The Flash and White Canary -lead their teams into battle to save the world.