Harkness threw a boomerang above a man's head, later identified as A.R.G.U.S. agent Kai Wu, letting it to return and stab the victim in the back.
Harkness used his boomerangs in his assault on A.R.G.U.S. offices for killing or injuring many security men and agents. He either threw the boomerangs towards the victims or used them as curved knives for slashing in hand-to-hand combats.
Harkness used one explosive boomerang with small charge during his fight against Oliver in train station.
- Curved blade: Sharpened from both sides with four prolongated holes in the boomerang's body.
- Optional: 3D-printed polymeric explosive boomerangs with sockets for C4 charges.
- Six boomerangs: Are worn on the front side of the jacket beneath the cloak of Harkness and at least two more somewhere else.
- Kai Wu, A.R.G.U.S. agent - killed
- Lyla Michaels, A.R.G.U.S. agent - seriously injured
- Employes of A.R.G.U.S., A.R.G.U.S. agents - killed or seriously injured