|The Prometheus Project, Part 1|
|Season 4, Episode 8 (68)|
|Superhero Club||The Prometheus Project, Part 2|
PART 2 OF 7: GRAND SCALE- As the Birds fight to escape the clutches of the Luthors, the maze of a facility through which they must navigate proves far more worrisome than first expected. Tess Luthor unleashes three new "Soldier Synths" on the team, while Nyssa Raatko faces her insecurities when she hallucinates her Earth-1 counterpart. Thea Queen discovers that Malcolm Merlyn is alive.
- Katie Cassidy Rodgers as Laurel Lance/S.I.R.E.N.
- Katrina Law as Nyssa Raatko/Nyssa al Ghul
- Jessica de Gouw as Helena Bertinelli/H.U.N.T.R.E.S.S.
- Willa Holland as Thea Queen
- Katie McGrath as Tess Luthor
- Chyler Leigh as Alexandra Danvers
- with Amy Acker as Brainiac
- and Katheryn Winnick as D.I.S.C.O.R.D.
Special Guest StarsEdit
- Michael Rosenbaum as Lex Luthor (Earth-30)/Lex Luthor (Earth-10)
- David Ramsay as John Diggle
- Audrey Marie Anderson as Lyla Diggle
- Colin Donnell as P.R.O.M.E.T.H.E.U.S.
- Kristin Kreuk as Evelyn Langstrom
- Deborah Ann Woll as Andrea Beaumont/The Phantasm
- Callum Blue as Greg Osborne/Black Arrow
- Sofia Boutella as Mercy Graves
- with John Barrowman as Malcolm Merlyn/A.R.C.H.E.R.
- and Brandon Routh as Ray Palmer
- Antagonists: Eobard Thawne, Lex Luthor (Earth-10), Leticia Luthor, Tess Luthor, D.I.S.C.O.R.D., Greg Osborne, Mercy Graves, Alexandra Danvers, S.I.R.E.N.
- 1st episode this season to feature all main characters.
- This episode takes place entirely inside the Prometheus Project compound.
- First appearances of S.I.R.E.N., A.R.C.H.E.R., and P.R.O.M.E.T.H.E.U.S..
- Nyssa al Ghul appears as a hallucination. She was last seen in Save My City.
- First present-day appearance of Malcolm Merlyn since Save My City.
- This episode takes place on March 4, 2020.