Dr. Dmitri Yuriev is one of the antagonists in the Xenosaga series, although he only really becomes antagonistic in Xenosaga Episode III: Also sprach Zarathustra in which he turns hostile to Shion Uzuki and her group. He is the head of the Yuriev Institute located on the planet Zavarov of star system Vartas. His life is dedicated mainly to the study and destruction of U-DO, and was the genetic father of all 669 U.R.T.V. units, including Rubedo, Albedo, Nigredo, and Citrine. U.R.T.V. unit 666 was the most powerful of his children with the most capabilities to defeat U-DO.