She was AI or Artificial Inteligent have body likely real Human. Originally named as AL-1S, Key is a mysterious member of Millennium's Game Development Department Club. She goes to Millennium science school. Found in an abandoned munitions factory at the Ruins, it's impossible to retrieve any information about her origin nor her age. She was another side Tendou Arisu, an AI whose role was to guide Alice to carry out a genocidal campaign in the name of the Nameless Priests.