Xenosaga Episode I
Xenosaga Episode II
Xenosaga Episode III
Xenosaga: Pied Piper


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Gender N/A [note 1]
Japanese VA Doug Erholtz
English VA Hikaru Midorikawa
Appearances Xenosaga Episode I
Xenosaga Episode II
Xenosaga Episode III
Xenosaga I & II
Xenosaga: The Animation

U-DO (Unus-Mundus Drive Operation (One World Drive Operation)) is a character in Xenosaga. It is an entity from the Upper Domain.


As U-DO is an entity from the Upper Domain, it has no physical form. U-DO often manifests itself as purplish-pink energy. Any human that comes in contact with it strikes them with a powerful fear, in Dmitri Yuriev's case, gain the ability to transfer his consciousness to other bodies. Many people refer U-DO as "God". Those who have a higher affinity with U-DO, usually those who descended from the Immigrant Fleet, allowing them to communicate with U-DO directly. However, this method of contact can cause extreme stress to the person and will cause the person to suffer from headaches and fainting spells before eventually falling into a coma.

Story arc[edit]


Dmitri Yuriev is the only human being to make contact with U-DO through the U.M.N. and survive, but the experience implanted him with an extreme fear of it. This fear is what prompted him to create the U.R.T.V.s in an effort to destroy U-DO. They were specially designed to combat U-DO, and can produce anti-waves designed to resist U-DO.

Shion's mother, Aoi was put in a coma due to her traits associated with the Immigrant Fleet and the people of the Zohar, causing her to have a high affinity with U-DO.

During the Miltian Conflict, the U.R.T.V.s manages to make their way into Labyrinthos and prepared to destroy it, but Unit 666, "Rubedo" experienced a vision of Miltia being destroyed by an explosion and prompted him to cancel the link. This caused U-DO's waves to kill or infect most of the U.R.T.V.s. Unit 667, "Albedo" was affected the worst as he made direct contact with U-DO, driving him completely insane. When Albedo came in partial contact with U-DO, he caused a space-time anomaly that created two black holes, sucking Miltia into one of them into the Abyss.

Episode I[edit]

Gaignun and Helmer express worry that the U-TIC Organization's plan for Old Miltia will result in U-DO's awakening saying it cannot awaken again. After the Kukai Foundation was framed by the U-TIC Organization, in a video conversation between Helmer and Wilhelm express the same worry.

In KOS-MOS's Encephalon, Nephilim shows the party a vision of the future where KOS-MOS encounters U-DO over Old Miltia, warning them that it will awaken again.

Episode II[edit]

While exploring the Submerged City, the party comes across some web-like biomass, revealed by Jr. to be U-DO's work. Near the end of the game, Albedo completes his contact with U-DO in a Space-Time Anomaly after Patriarch Sergius XVII's death.

Episode III[edit]

Throughout the game, Shion experiences several fainting episodes, due to her high affinity with U-DO, during these episodes, Shion experienced direct contact with U-DO and in one of the contacts, revealed that Abel is U-DO's physical form. Within her subconscious of Old Miltia, it is revealed by Kevin Winnicot, now the Red Testament that Shion is suffering from the same illness as her mother and will eventually die. On board Abel's Ark it is revealed that Yuriev has been infected by U-DO when he made contact with its waves. On Michtam, Wilhelm sealed away Abel and Abel's Ark using Joshua to prevent U-DO's observation of the universe, allowing him to perform the Eternal Recurrence.

Abel and Abel's Ark
Main articles: Abel (XS), Abel's Ark
Abel's Ark.

As U-DO dwells in the higher Upper Domain, it observes the Lower Domain through its observational terminals, Abel and Abel's Ark which function as U-DO's "eyes". While Abel is U-DO's physical form, many perceive U-DO as Abel while in the Lower Domain, Abel's Ark on the other hand does not exist in the physical realm, causing many to mistaken the Ark as a Gnosis.


Episode III


No image Database Thumbnail XS3.png

Mysterious waves that exist within the U.M.N.

The Unus Mundus Drive Operation System. Said to be a control AI originally created as a U.M.N. navigational device, it was refitted by Joachim Mizrahi as a Zohar command device

According to Vector records, the history of link experiments with U-DO extends back to the Lost Jerusalem era; apparently, it has been recognized as a wave-based existence since far before the development of the U.M.N.

Even today, details on U-DO has not been revealed. It is thought to be a consciousness from our own, and deeply intertwined with the space-time anomaly touched off by the Zohar and its going out of control.

The U-TIC Organization, knowing that certain people are able to make contact with this wave existence, gathered test subjects with this contact ability and conducted Zohar operational experiments.

They tried to use them to complete a so-called "U-DO system," but in the end, it merely led to the Zohar going out of control.



Episode I[edit]

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Episode II[edit]

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Episode III[edit]




  1. U-DO uses male pronouns in the English release, while the Japanese version uses 奴 (やつ, yatsu).