Ormus is an ancient religious cult that originated on Lost Jerusalem as Christianity. Members of Ormus seem to follow a blend of Gnostic Christianity and Catholicism, yet they believe that the Zohar is an artifact of divine intervention. They were the first to leave Lost Jerusalem via the Immigrant Fleet shortly before its downfall. In the setting of the Xenosaga series (set four thousand years in the future), Ormus continues to lust for the original Zohar on Old Miltia. Ormus uses a series of dummy corporations to extend its influence across the known universe. It serves as the core of the Immigrant Fleet, and also seizes control over U-TIC as a secret military arm after the Miltian Conflict. (In Xenosaga: Pied Piper, it is revealed that the people of the Immigrant Fleet are all of a special bloodline, and were once known as the People of Zohar.)
In Episode II, the Patriarch, leader of Ormus and the Immigrant Fleet, spearheads the operation to recover the Original Zohar and summon Proto Omega and the Omega System from the ruins of Old Miltia. Everything that Ormus' fronts did during Episode I and early Episode II culminated in this mission. The Patriarch planned on destroying the Gnosis with Proto Omega and ultimately place the entire star cluster under the jurisdiction of Ormus. Ormus' military organization, U-TIC, designed Proto Omega and the Omega System. However, fourteen years prior to Episode I, the system was sealed away with Old Miltia before the Patriarch could use it. Although he is on the edge of re-establishing his plan, the Patriarch is betrayed by Margulis and Heinlein. They abandon him on the Omega System, where he is killed by Wilhelm's Testaments. Proto Omega and the Omega System are destroyed, and the Original Zohar is sucked into Abel's Ark at the end of Episode II. In reality, the entire plan to seize the Zohar was just to bring Abel's Ark (one of the eyes of God, or U-DO) into this dimension with the help of Albedo and the recovery of the Zohar.
When Margulis betrays the Patriarch while working under Heinlein's orders, it makes Heinlein the highest ranking Cardinal in Ormus. In reality, Heinlein had all the true power in Ormus. It is clear that Ormus and all of its fronts are involved in the web of deception surrounding the Original Zohar, as Jin Uzuki pointed out in Episode II. Hyams Group, led by Heinlein himself (later to be revealed as the series' manipulator, Wilhelm), is also revealed to be the military supplier and major financial supporter of Ormus and its arms. Furthermore, despite his hatred of the U-TIC front, Dmitri Yuriev and his institute have connections to Ormus based on the fact that Hyams, the same group that funds Ormus, established it.
Followers of Ormus claim that they have been the guardians of the Zohar since recorded history. In turn, they use it in any way they see fit. They say that Ormus has existed before the crucifixion of the messiah (Jesus). In Episode III, Wilhelm reveals his true purpose for founding Ormus was to protect Lemegeton, also known as the "Word of Yeshua", that was left behind by a man who died thousands of years ago. The database states that chaos was the man who left this "word." The public purpose of Ormus was to preserve and spread the teachings of that man. Although according to Wilhelm, the man Ormus worshipped did not understand Lemegeton, because only chaos could understand it. Ormus were also the guardians of the Relics of God left behind in ancient times, such as Zarathustra and Merkabah.
Followers of Ormus claim that Planet Michtam is Ormus's birthplace. Since Ormus originated as Christianity about six thousand years prior to the game's storyline and Wilhelm claims he founded Ormus, Wilhelm may have altered Christianity to form Ormus on Planet Michtam. Of course, followers of Ormus also believed that their true purpose was to return to Lost Jerusalem (a lie that Wilhelm wanted them to believe), so the belief of Ormus being founded on Michtam may have also been another of Wilhelm's deceits.
Ormus is one of the names given to the supreme Zoroastrian god, Ahura Mazda, who represents truth and goodness. The physical world was created by Ahura Mazda as a place to battle against Ahriman, the spirit of evil. Ormus was also the name of a former kingdom that spanned the Strait of Hormuz at the mouth of the Persian Gulf, and this kingdom was also named after Ahura Mazda.
According to Holy Blood, Holy Grail, Ormus is a subtitle used by the Prieuré de Sion (Priory of Sion), the group that is supposedly responsible for the creation of the Knights Templar.