Both The Flash and Arrow will have quite a bit of ‘splaining to do in setting up Legends of Tomorrow through this week’s dual crossover, and we can officially check one item off the list. The source of Vandal Savage’s power is revealed in our first clip from The Flash opener “Legends of Today,” as outlined by our new Hawkman.

The CW released the first official clip from the two-part Legends of Tomorrow crossover, specifically The Flash half, despite taking place in the Green Arrow’s lair. In any case, a chained Hawkman (Falk Hentschel) outlines his connection to Kendra Saunders (Ciara Renee) and Vandal Savage (Casper Crump), while a new featurette also goes further in depth with the expanding universe:

So reads The Flash’s official synopsis for December 1 outing “Legends of Today,” followed on December 2 by Arrow installment “Legends of Yesterday”:

The Flash’s “Legends of Today”: In its second major crossover event with “Arrow,” Vandal Savage (guest star Casper Crump) arrives in Central City and sets his sights on Kendra Saunders (guest star Ciara Renée). After Vandal attacks Kendra and Cisco, they turn to Barry for help. Realizing how dangerous Vandal is, Barry takes Kendra to Star City and asks Oliver and team to hide her until he can figure out how to stop Vandal. However, things quickly go from bad to worse when a man with wings AKA Hawkman (guest star Falk Hentschel) shows up and flies off with Kendra. Meanwhile, Harrison develops a serum to make Barry run faster and asks Jay (guest star Teddy Sears) to test it out.

Arrow’s “Legends of Yesterday”: Oliver and Barry Allen take Kendra Saunders and Carter Hall to a remote location to keep them hidden from Vandal Savage while they figure out how to defeat him. Malcolm arranges a meeting between Vandal, Green Arrow and The Flash that doesn’t go as planned. Meanwhile, Felicity, Thea, Diggle and Laurel work with Team Flash to come up with a weapon powerful enough to destroy Vandal Savage.

Flash will kick off the crossover event Tuesday night, but what should we expect from the big Legends of Tomorrow setup? Check out the full photos and trailer set below.

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