Shadowspire was part of the U.S Army which later became is a terrorist group of war profiteers and an antagonistic faction in the fourth season of Arrow.
After a mission with John and Andrew Diggle, Lieutenant Joyner approaches the brothers, trying to recruit them to Shadowspire. Though declining the offer in front of John, Andrew secretly accepted it, profiteering from the war until he was discharged at which point Shadowspire cut ties with him.
Having obtained the map to Lian Yu, Reiter and Shadowspire head there. While growing a drug called Slam and harvesting it by the help of captured workers, Reiter's true aim is to find a magical artifact.
Later that night, Chang's corpse is found in an alleyway, missing three fingernails which leads Diggle to speculate he has been tortured for information. His torturers also cut out his left eye. Meeting with Waller, Layla and Diggle are told that this doesn't concern them. However, while shaking Layla's hand Waller hands Layla an USB drive containing information of Shadowspire.
After having found out that Shadowspire has come to Star City, John faces Andrew with the facts, asking him for how many secret organizations Andrew was working. Andrew tells him that he has nothing to do with Shadowspire anymore as they cut ties when he was discharged. He tells John that he can help them and tells them that they will use the nearest free port as hideout.
Heading there, Team Arrow defeats the Shadowspire soldiers guarding the outer perimeter, and then enter the warehouse. There, they search for the two missing agents. While searching a shipping container, Oliver is trapped when Felicity accidentally triggers a fail-safe which closes the container's doors. Meanwhile, Thea and Laurel find the missing two agents in another shipping crate, both dead. Inside the warehouse John is overpowered by Shadowspire soldiers and after he drops his gun, is approached by Joyner, now a high ranking operative. Joyner states that while he has heard much about the vigilantes, he has never seen on in person. John responds that he wishes the same would go for him with cold blooded murderers, causing Joyner to ask whether they have met before. However, Joyner and the rest of the soldiers are knocked out when Oliver blows up a wall of his container to escape. Diggle and Oliver then flee from the compound.
At the A.R.G.U.S. headquarter Waller tells Diggle that the two dead agents were guarding a shipment of electromagnetic rail guns. As this was a completely black assignment, Waller thinks that there has been a catastrophic security breach in her organization. However, Andrew Diggle, who has been brought to A.R.G.U.S., claims that the stealing of the rail guns was merely a distraction and that Shadowspire must be after something else.
While Team Arrow is dispatched to guard another shipment of rail guns, because Waller expects Shadowspire to strike again, Shadowspire soldiers enter the A.R.G.U.S. headquarter with the severed eye of Agent Chang. In there, they enter the control room, killing many A.R.G.U.S. agents. Forcing Waller to surrender, Joyner enters the room and demands that Waller gives them the codes to access Rubikon. When Waller does not give them the codes, Joyner orders his men to kill one of the surviving A.R.G.U.S. agents and tells her that he will ask her again in twenty minutes.
When Diggle reaches Oliver from the detention area, the broadcast is picked up by Shadowspire and Joyner sends a solider down to investigate. Two soldiers arrive at the cell Andrew Diggle is held in and ask him who he is.
When Waller makes it clear to Joyner that she would rather watch him execute every member of A.R.G.U.S. before giving him the codes, Joyner shoots Waller in the head and demands the codes from Layla. To save Layla and the rest of the agents, the both Diggle brothers produce a plan. Andrew, who was imprisoned at A.R.G.U.S. detention cells is brought before Joyner, who is surprised to see him, having believed him dead. Andrew tells him that he was imprisoned by A.R.G.U.S. for working with spitfire and tells Joyner that Layla is his sister-in-law. He tells Joyner that John is crawling around in the ventilation shafts and that Layla would give up the Rubicon codes if John's life were at stake.
The Shadowspire soldiers find John and force Layla to give up the code. When Layla, although trying, is unable to get into the computer as she is blocked out by Felicity, Joyner plans to shoot John but is attacked by Andrew. The rest of Team Arrow then appears and take out the Shadowspire soldiers, while Andrew knocks out Joyner after a fight.