Crisis on Earth-X is coming to The CW's Arrowverse this year and the crossover is not only offering some unsettling variations on familiar heroes, but the threat of a doomsday weapon as well. A new trailer for the event offers better details on what fans can expect when the doppelgängers invade and bring together the likes of Arrow, The Flash, Legends of Tomorrow, and Supergirl in order to take them down.

It has become an annual event for The CW that, in addition to being a ratings winner, gives the members of the various DC TV series a chance to interact with characters they otherwise wouldn't have an opportunity to, and for everyone to gather in one place, for the television equivalent of a massive splash page, as seen in the trailer above. And while every crossover has grown in both scale and ambition, Crisis on Earth-X looks to take the already huge undertaking up a notch, promising not only a massive collection of heroes over the two-night event, but a warped look at what the familiar heroes of the shows could have been had Germany won World War II. Think of it as the DC Comics version of Amazon's The Man in the High Castle.

Related: How Black Canary Would React To Oliver Being Green Arrow Again

That means stars like Melissa Benoist are pulling double duty, playing not only Supergirl but also her evil inter-dimensional counterpart, Overgirl. It also means that there'll be plenty of familiar and not-so-familiar guest stars showing up during the four-hour event, like a new version of Leonard Snart and Russell Tovey as the Ray. Aside from the guest stars, the promos have shown a brief glimpse at Overgirl's costume and a hint of what's to come when the two Girls of Steel clash with one another.

Crisis on Earth-X The CW

While the new promo goes all-in on the huge threat these twisted counterparts present, no one should overlook the fact that the impetus of the crossover is actually a celebration of Barry and Iris's wedding. This promo conveniently fails to mention that part of the story, which isn't too surprising given its emphasis on action, like the aforementioned Supergirl clash and what looks like the Flash clearing out a room of Nazi troopers.

In that sense, Crisis on Earth-X offers a classic comic book take on what is supposed to be a happy occasion, as the event is ruined by some very unwanted guests, putting a big question mark on the nuptials themselves even happening. The answer to that question should offer an exciting bookend to what looks to be the biggest Arrowverse crossover event yet.

Next: Arrow: Oliver Trusts Slade But Can’t Completely Forgive Him

Crisis on Earth-X begins with Supergirl and Arrow on Monday, November 27 @8pm, and concludes with The Flash and Legends of Tomorrow on Tuesday, November 28 @8pm on The CW.