Milo Armitage hired a man to free Ben Turner from prison by smuggling his claws inside his body. After Turner's escape, Armitage met with him and promised him $10 million to break into Malcolm Merlyn's vacant mansion and steal his prototype Markov Device. Turner did so, despite interference from The Arrow and Roy Harper, and met with Armitage to hand the device off to him. However, the Arrow and Roy arrived, and despite Armitage's best efforts, they destroyed the device and Armitage was arrested.
However, Armitage somehow got out from prison, presumably due to his connections.
Two years later, Armitage was revealed to be a high-ranking member of H.I.V.E., considered to be Damien Darhk's partners. Armitage sarcastically congratulated Darhk on becoming "famous" when Oliver outed Darhk as the mastermind behind H.I.V.E. and the Ghosts. Armitage and the other partners accompanied Damien when he nearly executed John Diggle, Felicity Smoak, and Thea Queen, but when Malcolm Merlyn and Laurel Lance interrupted, they fled. Later, Damien showed Armitage and the partners his progress with their operation, "Genesis".
When Damien was imprisoned, Merlyn visited him, informing him that Armitage and the other H.I.V.E. members had decided to move ahead with Genesis without him.
Armitage and Phaedra Nixon were present at H.I.V.E. headquarters when Damien returned, flanked by Merlyn, Andy Diggle, and Michael Amar, as he'd been freed from prison by the three. Nixon and Armitage were worried that Damien would seek vengeance for allowing him to rot in prison. However, Darhk seemed very calm, lulling the two into a false sense of security. Once Darhk learned that Genesis had continued without a hitch even during his imprisonment, he threatened the two, telling them he no longer needed them. Armitage promptly attempted to shoot Darhk, who used his telekinesis to deflect the bullet and redirect it into Armitage's forehead, killing him instantly. His body was later found by Team Arrow.