Legends of Yesterday

"Legends of Yesterday" is the upcoming eighth episode of the fourth season of Arrow and the seventy-seventh episode overall. This episode will crossover with the eighth episode of season two of The Flash. It will also set up upcoming series DC's Legends of Tomorrow, with the episode even introducing Vandal Savage, who will be the "big bad" of the series.

Cast

 * Stephen Amell as Oliver Queen/Green Arrow
 * Katie Cassidy as Laurel Lance/Black Canary
 * David Ramsey as John Diggle/Spartan
 * Willa Holland as Thea Queen/Speedy
 * Emily Bett Rickards as Felicity Smoak
 * John Barrowman as Malcolm Merlyn/Ra's al Ghul

Synopsis
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.

Production
Preparation ran from September 22 until September 30, 2015. Shooting began October 1, 2015 and ran until October 15, 2015.