Sergius XVII

Sergius XVII also known as the Patriarch is an antagonist in the Xenosaga series. He is the leader of Ormus and the Immigrant Fleet. Sergius is the primary antagonist of  Episode II.

Episode II
Sergius first appears in a scene where Margulis reports to him about the Y-Data falling into the hands of the Kukai Foundation and Miltian government. Margulis doesn't appear too concerned about it and says preparations for their next move are already under way. Sergius asks about the involvement of Heinlein, Ormus Cardinal in the recent offensive against Second Miltia but Margulis feigns having any knowledge about it. Sergius wonders if it is safe to trust Margulis' words and says he hopes to not be disappointed. He also expresses disgust over Albedo. Sergius later appears before the Federation Parliament as the representative of the Immigrant Fleet. He claims that mankind's greatest treasure is sealed away on Old Miltia and that the Immigrant Fleet had been its caretakers. He criticizes the Miltian government, claiming they are trying to claim the for themselves and had summoned Proto Merkabah to ignite flames of conflict across the galaxy. He proposes that in response to them, the Immigrant Fleet be able to reclaim its traditional rights as caretaker of the Zohar. Parliament members question some of his statements given the Miltian government clearing itself of recent charges of wrong doing, but also find that Miltian representative Helmer is absent.

After Albedo unlocks the seal to Old Miltia, Sergius leads the Immigrant Fleet in heading there to seize the Zohar. Sergius is again seen speaking to Margulis about ensuring they fight off any interference from the Miltian Government, Subcommittee on Close Encounters and Vector. When the party makes its way to Old Miltia and into the depth of Labyrinthos where the Zohar is stored, Sergius appears before them. He tells them that the Zohar originally belonged to Ormus, which acted as its guardians. He believes that all life must be guided forward by Ormus and the Zohar. He activates the Zohar, along with Proto Omega. He proclaims that possessing them, Ormus will be able to wipe out the gnosis from the cosmos and put the entire star cluster under their jurisdiction. He also proclaims the masses to be spineless weaklings due to the influence of the U.M.N. and Federation. He departs with Proto Omega and the entire planet of Old Miltia is destroyed as the Ω System appears.

Despite holding overwhelming power, Sergius is soon after betrayed by Margulis, who refuses orders to fight off the approaching Federation fleet and has conspired along with Heinlein for Sergius to die a martyr. The party makes their way through the Ω System and confronts Sergius at its center. Albedo appears, but is unable to harm Sergius, who fires Proto Omega's U.M.N. Phase Transfer Cannon at him, causing him to disintegrate. After the party fights and defeats him, Sergius plans to use Proto Omega's Cannon on them as well, but its power halts suddenly. Three E.S.s piloted by the Testaments appear and claim it is time for him to exit the stage. They fire at Sergius and he is vaporized.

As a boss

 * Patriarch