In “Arrow” season 4 episode 20, Oliver Queen goes to another city to find someone who can help him fight Damien Darhk’s magic while John Diggle confronts Andy and Thea goes on a vacation only to realize that something is off.
Green Arrow’s visit to Hub City
Damien Darhk disposes Milo Armitage and Phaedra Nixon and begins the final phase of something called “Genesis,” the biblical title of the episode. Meanwhile, Oliver advised the team not to go against Darhk until they find a way to counter his black magic. At the counsel of John Constantine, Oliver must go to Hub City and train under a magician who can repel dark magic. Should the training prove successful, will the Green Arrow finally take down Damien Darhk for good?