- "Vengeance and retribution are useless pursuits. For one thing, they don't pay."
- —Joyner on his life philosophy[src]
Lieutenant Joyner is a high-ranking member of Shadowspire and a military lieutenant of the U.S. Army who formerly served in Afghanistan. After the death of Baron Reiter and the defeat of Shadowspire at the hands of Alan Chang, he re-gathered the seemingly destroyed group and staged a terrorist attack on A.R.G.U.S., intent on enacting revenge on Amanda Waller and stealing Rubicon.
Time in Afghanistan
In 2005, Joyner served as a Lieutenant stationed in Afghanistan along with two privates, Andy and John Diggle. Realizing that the two brothers deserved to move on to better things, Joyner tempted them with the offer of confiscating opium from Afghanistan to earn money. Andy, putting on a front for his older brother, stuck to his morals and shot down the offer but was later caught by John shaking hands with Joyner and passed it off as simply teaching him a blackjack card counting technique. Joyner also traded the stolen opium to his boss, Baron Reiter, in exchange for Slam found on Lian Yu. 
Payback on A.R.G.U.S.
While walking home from a date, John and his wife Lyla Michaels witnessed Chang being shot in the back and abducted by Shadowspire who mutilate him by removing an eye, pulling off his fingernails and lacerating him. Two other A.R.G.U.S. agents that were abducted were later found dead by Team Arrow. Andy, knowing how Joyner and Shadowspire operates, revealed to Amanda Waller, Diggle and Lyla that Joyner and Shadowspire are using the Railgun stealings as a diversion for their endgame. Using Chang's eye, Joyner and Shadowspire infiltrated the A.R.G.U.S. headquarters and demanded Rubicon access codes from Waller, who admitted that she won't break even if everyone in the room is killed. Realizing that this is case after Lyla admitted that Waller doesn't make decisions based on the value of human lives, Joyner shot Waller in the head and demanded Lyla to give him the codes. The Diggle brothers managed to work together in order to stop Shadowspire long enough for Team Arrow to arrive. Andy saved John from being shot by Joyner, who he managed to beat in a fist-fight.
Joyner is a ruthless war profiteer, with nothing but pragmatic ways of getting more profit on his mind. He is a good judge of character, being able to convince Andy Diggle to join Shadowspire, as well as deciding to kill Amanda Waller, realizing that she won't reveal the location of Rubicon no matter how many people he threatens to kill before her eyes. He saw dealing in drugs as a viable method of profiteering. Joyner was able to hide his motives, making his enemies think that Shadowspire is after revenge for its defeat by A.R.G.U.S. operatives. In reality, the revenge, as well as the attempt to grab the arsenal of rail-guns was but a ruse to cover Joyner's real goal – infiltration of A.R.G.U.S. headquarters in search for Rubicon and its access codes.
- Peak of human physical condition: As a former soldier, Joyner is in top physical condition.
- Military training: Joyner served in the army and received extensive military training.
- Master tactician/Leader: As the leader of Shadowspire and former high-ranking soldier, Joyner is capable leader and presumably great tactician.
- Expert hand-to-hand combatant: Joyner has displayed proficiency in hand-to-hand combat.
Behind the scenes
- Joyner is likely a reference to Tom Joyner, a comic book writer, who created the Shadowspire organization in his comics, depicting them as enemies of Slade Wilson.