Arrow 5×23 “Lian Yu” Season 5 Episode 23 Promo (Season Finale) – DEATHSTROKE, NYSSA AL GHUL, MERLYN AND DIGGER HARKNESS JOIN OLIVER’S BATTLE AGAINST PROMETHEUS – The battle between Oliver (Stephen Amell) and Adrian Chase (Josh Segarra) culminates in a final epic battle on Lian Yu. After recent events, Oliver decides to recruit a group of unlikely allies – Slade (guest star Manu Bennett), Nyssa (guest star Katrina Law), Merlyn (John Barrowman) and Digger Harkness (guest star Nick. E. Tarabay) – to defeat Chase. However, Chase has his own army – Black Siren (guest star Katie Cassidy), Evelyn Sharp (guest star Madison McLaughlin) and Talia al Ghul (guest star Lexa Doig) – and the forces collide in an explosive season finale. Jesse Warn directed the episode written by Wendy Mericle & Marc Guggenheim (#523). Original airdate 5/24/2017.