A guardian angel to those who come under her care, Dr. Angela Ziegler (Callsign: Mercy) is a peerless healer, a brilliant scientist, and a staunch advocate for peace. Ziegler rose to become the head of surgery at a prominent Swiss hospital before pioneering a breakthrough in the field of applied nanobiology that radically improved the treatment of life-threatening illnesses and injuries. It was this expertise that attracted the attention of Alliance. Because her parents had been taken by war, Ziegler was opposed to the organization's militaristic approach to keeping global peace. Ultimately, she recognized that Alliance offered her the opportunity to save lives on a much larger scale. As Overwatch's head of medical research, Angela sought to leverage her work for healing in frontline crises. The result was the Valkyrie swift-response suit, which Ziegler herself piloted on many missions in the timeline.