Alex Mercer is a shapeshifting entity and protagonist of the video game Prototype. He is a lethal and manipulative antihero who battles the parasitic virus Blackwatch, which aims to control New York City. Known for his adaptive powers and tactical intellect, Alex is a complex individual with a violent history that's a stark contrast to his empathetic core, where he often grapples with his own humanity and the ethics of his actions. His primary antagonists include Blackwatch operatives such as the rational scientist Dr. Ragland and the ruthless Colonel Douglas Mercer. Alex's drive is fueled by the loss of his sister, who he failed to protect from Blackwatch, and the subsequent infection that resulted in his transformation into a parasitic-like entity. Beyond his powers, Alex has a protective streak for the citizens of New York City, whom he considers his responsibility.