Nigredo
He was maybe the U.R.T.V.s who was the closest of, their powers and reason to exist being the same. She is the one who revealed him about his purpose and powers, but never revealed if she knew what Yuriev really created him for, and likely met him more often that the others variants. She saved her life at two time, one nearly killing her, when they were kids. She never said her thought on Yuriev's using Gaignun's body, but could speak to Gaignun few after the first time Yuriev used him, and said he had to serve her father. It is likely she was lead to think Gaignun by himself was dead, and mere remant of memories remained inside the body, since she claims Rubedo to be her last 'comrade' alive even though Gaignun still is.
After her death, Yuriev has a 'discussion' with Gaignun's consciousness, where we learn he is sad of her death and that he had a 'Connection' with her. The nature of this connection in unknown and is left up to imagination.
Yuriev
Yuriev was her father. She was raised to think his actions are right and nearly followed him blindly in his actions, though in the end she doesn't do it for him, but because it is her reason to exist and has nothing else left. Maybe her life could have been different if she met people disliking Yuriev and who taught her things of life. Yuriev consider her as a mere unit, as he does for each U.R.T.V.s.