With "The Flash" and "Arrow" two-part crossover less than two weeks away, The CW has released a new, minute-long extended trailer for the episodes, which are jointly known as "Heroes Join Forces." (SPOILER WARNING: The teaser does include a brief synopsis of the Hawks' origin story.)

The episodes serve as a prelude to the upcoming "DC's Legends of Tomorrow," the third CW series set in the Arrowverse. Casper Crump will debut in the crossover as long-running DC Comics villain Vandal Savage, who will be the primary "Legends of Tomorrow" antagonist.

The "Flash" half of "Heroes Join Forces," "Legends of Today," airs at 8 p.m. Tuesday, Dec. 1. The "Arrow" half, titled "Legends of Yesterday," airs 8 p.m. Wednesday, Dec. 2. Here's the official network description of both episodes:

"Legends of Today"

PART ONE OF THE EPIC CROSSOVER WITH "ARROW" - 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 Renee). After Vandal attacks Kendra and Cisco (Carlos Valdes), they turn to Barry (Grant Gustin) 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 (Tom Cavanagh) develops a serum to make Barry run faster and asks Jay (guest star Teddy Sears) to test it out. Ralph Hemecker directed the episode with story by Greg Berlanti & Andrew Kreisberg and teleplay by Aaron Helbing & Todd Helbing (#208).

"Legends of Yesterday"

PART TWO OF THE EPIC CROSSOVER WITH "THE FLASH" - Oliver (Stephen Amell) and Barry Allen (guest star Grant Gustin) take Kendra Saunders (guest star Ciara Renee) and Carter Hall (guest star Falk Henstchel) to a remote location to keep them hidden from Vandal Savage (guest star Casper Crump) while they figure out how to defeat him. Malcolm (John Barrowman) arranges a meeting between Vandal, Green Arrow and The Flash that doesn't go as planned. Meanwhile, Felicity (Emily Bett Rickards), Thea (Willa Holland), Diggle (David Ramsey) and Laurel (Katie Cassidy) work with Team Flash to come up with a weapon powerful enough to destroy Vandal Savage. Thor Freudenthal directed the episode with story by Greg Berlanti & Marc Guggenheim and teleplay by Brian Ford Sullivan & Marc Guggenheim (#408).