The CW has released a new promo video online for the final episode of the season for The Flash and Arrow. It features Arrow introducing the Flash to a an underground, superhero fight club, where heroes and villains go to "blow off steam".
It seems to be a promotional tool to better promote some of the heroes and villains for the spin-off. But it's pretty awesome anyway.
It features The Flash, The Canary, Arsenal, The Arrow, The Dark Archer, Ra's al Ghul, Captain Cold, Heatwave, Reverse-Flash, Martin Stein, and the whole Firestorm Matrix. Though it unfortunately didn't feature The Atom fighting. But it was a hilarious short teaser anyway.
The CW have also released the first three in what are most likely a series of posters which seem to be connected to the "Superhero Fight Club" promotional spot.