The CW's epic four-night "Invasion!" crossover event is imminent. The heroes of "Supergirl," "The Flash," "Arrow" and "Legends of Tomorrow" are set to take on the menace of the alien Dominators next week, and to whet viewers' appetites for what promises to be the "best team-up ever," the network has released a new promo video.RELATED: Arrowverse Crossover Will Reveal New Information About Flash’s FutureThe only person who doesn't seem psyched in the clip is "Arrow's" Oliver Queen (Stephen Amell), but that's probably because he and "The Flash's" Barry Allen (Grant Gustin) appear to be facing the possibility of an alien attack on Star City itself -- that's the kind of thing can really hurt a mayor's chances at re-election!

As part of their promotion The CW have also released a tetraptych crossover poster featuring all four of the network's DC Universe shows via the @TheCWProvidence Twitter account.

Starring Melissa Benoist as the Girl of Steel, “Supergirl” airs Mondays at 8 pm ET/PT on The CW. The network is also home to Grant Gustin as the Scarlet Speedster in “The Flash,” airing Tuesdays at 8 pm ET/PT, Stephen Amell as the Emerald Archer in “Arrow,” airing Wednesdays at 8 pm ET/PT and Arthur Darvill, Brandon Routh and Caity Lotz in “DC’s Legends of Tomorrow,” airing Thursdays at 8 pm ET/PT.