Mickey Duka was a subordinate of Howard Saint and a small-time crook on his own. He was also a friend of his boss' younger son, Bobby Saint. He convinced the latter to participate with him to a weapon trade with Otto Krieg, a new merchant. The meeting went wrong and the police broke in, and in the following gunfight Bobby was killed and Mickey got arrested.
Although being in jail, Duka was immediately freed and taken to Saint's home, where Quentin Glass tortured him in order to punish him for Bobby's death. Howard himself tried to kill him, but let him alive when he was told who the contact of Bobby was, and later discovered that, under the identity of Otto Krieger, was hiding the FBI agent Frank Castle.
Some time later, when Castle's family had been wiped out, Mickey Duka was kidnapped by The Punisher, who frightened him by making him believing he was been tortured. Almost immediately, Duka declared that he actually hated the Saints and freely agreed to help the vigilante to kill them all. Mickey started to manipulate Howard, following Frank's instructions, and managed to convince him that his wife was cheating him with his best friend. When the Saints were killed, Mickey was the only subordinate left alive by The Punisher and heir to Howard's club.