Slade Wilson was part of a military unit that got stranded on the South Pacific island of Lian Yu. He found another castaway named Oliver Queen and taught him military tactics and hand-to-hand combat techniques, which aided them in conflicts against people such as Edward Fyers and Anthony Ivo. Slade developed a romantic interest in a young woman named Shado. When Slade was injured during an incident with Ivo's people, Oliver Queen and Shado made a risky and desperate act to save him by injecting him with an experimental Japanese drug called Mirakuru. Slade survived and healed from his injuries, and even developed enhanced physical strength and reflexes. Unfortunately, the Mirakurualso drove him insane. When Ivo killed Shado, Slade blamed Oliver Queen for her death, swearing that he would get revenge upon him. During a fight between the two, Oliver took out Slade's right eye.
Slade Wilson eventually got off of Lian Yu and tracked Oliver Queen back to Starling City. As part of his obsessive scheme to destroy everything Oliver loved, he mass produced Mirakuruto create an army of super-strong soldiers. Through a protégé, Isabel Rochev, Wilson was able to take control of Oliver's company, Queen Consolidated, infect Ollie's partner, Roy Harper with Mirakuru, stabbed Oliver's mother, Moira Queen, through the heart, killing her. After finally overpowering Slade Wilson in combat, Oliver brought him back to Lian Yu and put him into a special underground solitary confinement cell.