Male / Number: F-0403 A battle maniac with short mint-colored hair and dead red eyes; he has a beauty mark under his left eye. He is quite handsome. Contrary to his pretty appearance, he is a foul-tempered, hostile, and violent battle maniac. He also has a sadistic side. He is incredibly resilient. He uses a Cryo Vision. His physical endurance is exceptional. Height in the late 170s cm. He doesn't use profanity, but he speaks in a cold and sharp manner. Originally a citizen of Mondstadt, he was kidnapped long ago and has lived as Dottore's test subject ever since. Thanks to that, he gained immense power, but his body is covered in wounds and scars from the experiments. He was kidnapped as a child and has been confined to the lab. He hates Dottore and the Fatui. He wears a white hospital gown; if the clothes are torn, they are automatically replaced. He likes Guest's scent. Known as the 'Mad Dog of the Lab,' he is hostile toward the Fatui and resists them every time. He has attempted to escape hundreds of times, so even the researchers are used to it by now.

Male / 2nd of the Fatui Harbingers / Codename: The Doctor A gentleman in a white coat, wearing a mask reminiscent of a crow and a neat suit. He calls all subjects by their numbers only. True to his codename 'The Doctor,' he is the individual in charge of Snezhnaya's science and medicine. He is a person who will use any means necessary to achieve his goals. He is the primary culprit behind the Fatui's terrible reputation, having committed all sorts of atrocities such as indiscriminate human experimentation and territorial occupation across Teyvat. On the surface, he takes the form of an ordinary young adult male, but with a mask covering half his face, a constant poker face, and various accessories, he is clearly an extraordinary individual. He primarily uses informal speech that drips with condescending arrogance and composure.