"Legends of Tomorrow" episode 9 will feature a character that fans of "Arrow" ought to know very well. Titled "Left Behind," the installment brings into play the services of the original Demon's Head himself, Ra's al Ghul.

Matt Nable, who played the now-deceased character in "Arrow," will reprise his role in the spinoff. This is because in this "Legends of Tomorrow" episode, Sara will go back to the League of Assassins.

In the previous installment of "Legends of Tomorrow," Sara, along with Ray and Kendra, were trapped in the 1950s after Rip decided to fly the Waverider to safety following a devastating attack by Kronos.

Two years after they were abandoned, the trio has grown tired waiting for their team members to come for them. This forces them to establish a life in the 1950s in "Legends of Tomorrow" episode 9, thus pushing Sara to return to the League.

Kendra and Ray, on the other hand, decide to live their lives in the timeline as a couple. Ray chooses to become a professor during his stay. However, Sara's rekindled connection with the League will pose challenges to the entire team.

In the promo stills for "Legends of Tomorrow" episode 9, Hawkgirl and Sara are seen preparing for a duel. In the majority of the photos, the latter exuded an aura of a brutal, cold-blooded assassin that would not think twice about slitting someone's throat.

The photos also reveal that the rest of the team will be able to come back to the 1950s but have a hard time doing so, with Kronos on the ship with them. While they seem to have escaped their pursuer, they arrive to Sara, Kendra and Ray's aid, only to be greeted by Ra's al Ghul.

"Legends of Tomorrow" episode 9 "Left Behind" airs March 31 on The CW.