U.R.T.V.
From Xenosaga Wiki
U.R.T.V. units, or "U-DO Retro Virus" units, are a series of biological weapons whose life energy wavelength cancels that of U-DO. They are the biological children of Dr. Dmitri Yuriev, head of the Yuriev Institute. U.R.T.V's were genetically engineered from the egg of anonymous female donors. U.R.T.V. units 666 - 669 originated from the same embryonic culture as the others, but were then subjected to an induced mutation to develop their unique gifts. This accounts for the differences in hair and eye color despite their shared embryonic origins. These four mutants are known as the Variants. The blond, standard U.R.T.V. Units 001 - 665 share one collective consciousness, and regard units 666 - 669 as "monsters" due to being mutants with individual minds. Most female U.R.T.V.s are unstable and usually die.
Unit # 666 is nicknamed "Rubedo" and is the leader of the male U.R.T.V.s. His special power is that he can control the rate of growth of his cells. Unit # 667 is nicknamed "Albedo". His special power is "the infinite telomerase" - the ability to regenerate his cells very quickly and without limit on the times done so. Unit # 668 is nicknamed "Citrine" and is the leader of the female U.R.T.V.s. Unit # 669 is nicknamed "Nigredo". His special power is the ability to hypnotically manipulate people. Units #666 and #667 were conjoined twins who were connected at their backs around their right sides until the 28th Week after conception. Given the nature of conjoined twins this was either natural or part of some advanced form of medicine.
chaos made an allusion in Xenosaga: Episode II, insinuating that the four variant U.R.T.V.s are the Four Horsemen of the Apocalypse in the Xenosaga universe. Albedo is the white rider "Pestilence", Rubedo is the red rider "War" and Nigredo is the black rider "Famine". However it is not known who Death is. Most assume that Citrine is the pale rider, Death, as she is the fourth U.R.T.V. variant. This comment is believed to be completely symbolic, as none of the U.R.T.V variants have displayed characteristics in line with the Four Horsemen of the Apocalypse.
U.R.T.V.s can produce anti-waves designed to resist U-DO, but these anti-waves will not neutralize each other. The waveform collision between these anti-waves will release enormous amounts of thermal energy, resulting in the destruction of anything near them, including the U.R.T.V.s. A moment before the U.R.T.V.s were to destroy U-DO, Rubedo had a vision of the Old Miltian planet being destroyed in an enormous explosion. Rubedo, fearing for the lives of his companions, broke the psychic bond that would produce the anti-waves. Unfortunately, this left them with no protection against U-DO. U-DO caused the deaths of or drove mad all of the standard U.R.T.V.s. It then infected Albedo and drove him mad as well. The only documented surviving U.R.T.V.s were Nigredo and Rubedo, though Albedo survived as well. It was learned in Episode III that it would have been impossible for the U.R.T.V.s to destroy U-DO, as it cannot be destroyed. It might have been possible, however, to destroy U-DO's observation terminals, Abel and Abel's Ark.
