When Lex Luthor was called upon to deal with a peace treaty in North and South Rhelasia, Mercy accompanied him as his bodyguard. At first she acted solely as his silent personal assistant, but when Cheshire and Sportsmaster attacked, she revealed herself to have a cannon stored in a cybernetic arm, and took an assassin down.
When the Light decided to finalize their plans of coercing Superboy, Miss Martian and Artemis, Mercy made sure Luthor was safe. The evening did not go as planned, and Mercy had to fight off Aqualad to allow her boss to escape with the unconscious Queen Bee.
Mercy went through several papers with Luthor, including one revealing Speedy had left his hospital bed. Moments later, they were startled by a rocket, fired from an adjacent rooftop. Both made it safely under Luthor's desk in time.
Mercy was concerned with Luthor's safety, but he insisted on getting a briefcase from his vault first. She then led him to the car parking lot. Speedy confronted them, and ordered them to disarm. Instead, Mercy attacked him. The fight went on for some time, with Mercy on the offensive. Speedy beset her with several types of weapons, both ranged and close combat, and eventually defeated her. He coiled LexCorp detonation cord around her cybernetic arm and blew it off, sending Mercy into a nearby car.
Feeling an explosion, Lex had Mercy perform a frequency override on the security cameras, revealing Alpha Squad's presence. Mercy went to call in security, but Lex stopped her, saying it would be redundant.
Cybernetic arm: Mercy's right arm has been replaced by a cybernetic enhancement. In its normal mode, it has a normally functioning hand, but it can be folded outwards to reveal a powerful beam weapon. The arm was destroyed by Speedy.