Mister Hammer, also referred as Mr. Abramovici, is The Joker's one armed lieutenant in his army. He was mentioned to be with his conjoined twin, Sickle, performing at a Russian circus. They got into an argument and split up, joining separate factions in Arkham City.
When Batman goes in Joker's Funland and tries to find Joker, who remotely tried to assassinate Catwoman, he goes in the vents and tries to surprise the Joker, but he comes into the middle of Harley's announcement. She explains to her group that Dr. Stacy Baker failed Mr. J and that she couldn't cure him. Baker pleads that she couldn't do anything, but Harley calls her a quack, and then kicks her from Joker's office onto the floor below. Harley announces "Do you want to see a show?" and they start to chant "Kill," as Mister Hammer tries to kill her with his sledgehammer, but she starts to crawl away. As soon as Mister Hammer got her cornered, Harley stops him by saying that the Joker needs her alive, so she can get tortured more. The thugs dragged her away, as Batman follows them, going through a bunch of thugs.
After saving Stacy Baker and getting the Remote Electric Charge, he makes his way to Joker's office, where Harley locks the doors from him getting in. Yet, by using the REC, he knocks the steel doors, blocking him from the Joker. Harley yells at him for knocking the steel doors, but as soon as he grapples up to the office, Mister Hammer kicks back down to the floor. Harley says, "Meet Mister Hammer. Heis going to teach you some manners." After fighting Mister Hammer and a bunch of thugs, he wins and makes his way towards Joker, yet he finds him dead and Harley crying. However, it was just a gag and Harley knocks out the Bat, with her bat.
Mister Hammer later again fought Batman alongside with a TITAN Henchman and Joker's thugs, and was ultimately sounded defeated by the Dark Knight.
After the Joker's death, Mister Hammer was reunited with Sickle at the Steel Mill, talking about how they wanted to be together again. Mister Hammer soon later work for Black Mask and came into conflict with Robin during the apprehension of the former's boss. 
- Mister Hammer has a Hammer and Sickle "☭" tattoo, a symbol formerly used by his country, Russia whilst Part of the Soviet Union. It is also fitting for him and his brother, due to their names and weapons respectively. 
- 9 Appearances of Mister Hammer (Arkhamverse)
- 2 Images featuring Mister Hammer (Arkhamverse)
- Quotations by or about Mister Hammer (Arkhamverse)
- Character Gallery: Mister Hammer (Arkhamverse)
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