Mono. He is called this because of his serial number, 3020 (it's on his arm). If you write that vertically it looks like "Mono". I'm unsure of his precise backstory details right now but he is sentient (infected with the MorningChorus virus). He is a former guard of Selaphiel (evil mantis priest popstar robot) but now he protects the Archive or whatever it's going to be called, which is a sort of robot hive mind thing.