Barry and Iris’s wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony. All of the superheroes band together with help from their super friends like Citizen Cold, The Ray, Felicity Smoak, Iris West and Alex Danvers to take on their most formidable villains yet. Earth’s mightiest heroes – Green Arrow, Supergirl, The Flash and White Canary – lead their teams into battle to save the world.
The battle between Oliver and Adrian Chase culminates in a final epic battle on Lian Yu. After recent events, Oliver decides to recruit a group of unlikely allies — Slade, Nyssa, Merlyn, and Digger Harkness — to defeat Chase. However, Chase has his own army – Black Siren, Evelyn Sharp, and Talia al Ghul.
Black Siren returns to help Chase. Felicity organizes a birthday party for Oliver while Lance is furious after Rene misses the custody hearing for his daughter.
Oliver returns to the mayor’s office and faces one of his most pressing issues yet – the forced release of dozens of violent criminals prosecuted by Adrian Chase. Meanwhile, a crate is delivered to Oliver’s office containing a mysterious corpse encased in concrete.
Things get intense when Oliver and Felicity are trapped in the bunker together. Meanwhile, Lyla and Diggle deal with their marital issues.
Oliver, Team Arrow, ARGUS and the SCPD kick off a citywide manhunt for Adrian Chase. Helix tells Felicity they have a way to find Chase but they will need something big, and illegal, from her in return.
Diggle and Felicity are shocked by Oliver’s decision to call on the Bratva to help take down Prometheus. Concerned the Bratva may overstep, Diggle has a hard conversation with Oliver about what happens if things go south. Meanwhile, Felicity learns something shocking at Helix.
Prometheus goes to great lengths to break Oliver. Meanwhile, in the flashbacks, Anatoly becomes worried about Oliver’s increasingly violent tendencies, which come to a head in a brutal confrontation.
Oliver gets closer to the truth about Prometheus. Meanwhile, Helix refuses to continue helping Felicity until she does a favor for them.
Oliver faces his biggest challenge yet as mayor. Felicity continues down her dark path with Helix. After Vigilante attacks Oliver while he’s acting as the mayor, Diggle leads the team in a mission to stop Vigilante once and for all.