Warning: Potential spoilers for the "Arrow" season finale.

The CW (via Green Arrow TV) has debuted the first official image from the season finale of "Arrow" and it confirms that Katrina Law will return as Nyssa al Ghul for the episode.

"[Sara] went to go get help, because when you're fighting an army, you need an army," Andrew Kreisberg told the site. "She goes and gets Nyssa, and she comes back with the League. It's the Arrow, Canary, Roy and the League of Assassins vs. Slade and his Mirakuru army for the city."

Titled "Unthinkable," the episode is described as follows:

"Slade moves forward with his plan to kill one more person in Oliver’s life. While Oliver has fought all year to be more than the killer he once was, when Slade kidnaps someone close to Oliver’s heart, Oliver is pushed to the edge and realizes sometimes it takes doing the unthinkable to stop the monster. Meanwhile, Diggle takes on Amanda Waller with a little help from some friends, and Thea turns to Roy in her time of need."

Directed by John Behring with story by Greg Berlanti and teleplay by Marc Guggenheim & Andrew Kreisberg, "Unthinkable" is set to air on May 14. "Arrow" airs Wednesdays at 8 P.M. ET/PT on The CW.​​​​