Darth Millennial, who possessed three eyes, was a mutant Sith Lord belonging to the Shadow Hand order. As an heir to Darth Bane's legacy, he existed nearly a millennium prior to the Battle of Yavin. Serving as an apprentice to Darth Cognus, Millennial wielded significant power in the Force and could perceive future events. However, disagreements with his Master regarding the Sith way led to disillusionment with the Rule of Two, which he considered excessively limiting; he found greater value in Lord Kaan's Rule by the Strong.
Ultimately, he abandoned his angered Master and established the Dark Force religion, which later evolved into the Prophets of the Dark Side on the planet of Dromund Kaas. By declaring himself a prophet chosen by the Force, he attracted numerous Force-users from across the galaxy to his religious movement before his death.
Millennial, a Human mutant distinguished by his three eyes, lived approximately one thousand years before the Battle of Yavin. At some point, he was drawn to the dark side of the Force, leading him to join the Order of the Sith Lords. He became the apprentice of Darth Cognus, a female Iktotchi Dark Lord of the Sith and a staunch advocate of Darth Bane's Rule of Two, which mandated the existence of only two Sith: a Master and an apprentice. Millennial demonstrated exceptional talent in using the Force, displaying potent precognitive abilities and training as a Shadow Hand under Darth Cognus.

Despite his Force abilities, Millennial and Cognus held differing views on the Sith, particularly concerning the Rule of Two. Millennial consistently questioned established teachings and strongly opposed the Rule of Two's philosophy, finding it overly restrictive. Instead, he favored the more combative approach promoted by Lord Kaan, a former Dark Lord and founder of the Brotherhood of Darkness: the Rule by the Strong, which advocated for a larger number of Sith with leadership determined by strength. His Master rejected this concept, leading to frequent clashes during his apprenticeship. Ultimately, tensions escalated, and Millennial deserted his Master, seeking refuge on the distant planet Dromund Kaas to escape her wrath. Cognus selected a new apprentice and continued the Rule of Two lineage, while Millennial began establishing his own dark side religion on Dromund Kaas.
Settling on the swampy world, Millennial dedicated himself to contemplating and refining Kaan's ideas. By integrating them with the teachings of two Pre-Republic era philosophers, Plaristes and Dak Ramis, Millennial created a unique religion called the Dark Force and resided in a temple within Dromund Kaas's swamps. He proclaimed himself a prophet chosen by the Force and invited Force-users from across the galaxy to join him on Dromund Kaas and become initiated into the Dark Force. Many Force-sensitive individuals from diverse backgrounds, along with numerous naive Sith cultists, joined him, attempting to maintain secrecy about the religion. Those who did not believe in the Dark Force were vilified as heretics, and Millennial and his religion encouraged their elimination. Millennial became the Supreme Prophet of the Dark Side, and his organization issued numerous prophecies during his lifetime.
Although Millennial eventually died, his religion persisted. Practitioners of the Dark Force became known as Prophets of the Dark Side, and the order remained secluded on Dromund Kaas for centuries, hidden from the Jedi Order and the Galactic Republic. The Prophets eventually attracted the attention of Darth Sidious, who recruited them as advisors in his roles as Supreme Chancellor and Galactic Emperor. After Sidious's Inquisitors attacked the Prophets, they fled to Bosthirda. A trio of darksiders eventually destroyed Millennial's order: Azrakel, a former student of the Prophets; Lumiya, the Dark Lady of the Sith; and her apprentice, Carnor Jax. By the conclusion of the Yuuzhan Vong War, they had not been openly re-established. Following the Battle of Endor, a false group of prophets emerged, using the ancient prophecy about a three-eyed mutant rising among the prophets to promote Trioculus, a slave lord, as the new Emperor. However, these false prophets were also eliminated.
The New Jedi Order knew of Millennial's existence, and after the Yuuzhan Vong invasion, Jedi Master Tionne Solusar published a series of texts that mentioned him. However, the New Jedi Order possessed limited information, primarily knowing that he founded the Dark Force.
Millennial was not one to blindly accept authority, instead questioning everything he learned and forming his own opinions. He believed in strength in numbers and felt that the Sith would prosper under the Rule by the Strong. He believed that the strongest member should lead and that anyone who surpassed the leader in strength had the right to take command. Millennial was a strong leader himself, persuading numerous dark side followers to abandon their orders and join him on Dromund Kaas.
Millennial possessed great confidence in himself and his abilities, particularly his precognitive powers, believing himself special enough to be chosen as the prophet of the Force's will. However, despite his confidence, he knew when to retreat. After his disagreements with his Master regarding Sith governance escalated, he recognized her superior power and went into hiding. Millennial had pale skin and a black-and-silver beard. He had two blue eyes and a yellow third eye located in the center of his forehead.
Abel G. Peña created Darth Millennial before 2001 for Evil Never Dies: The Sith Dynasties, an article discussing various lesser-known Sith organizations. The article described Millennial as a "three-eyed mutant," retconning him as the Dark Lord mentioned in the children's novel The Glove of Darth Vader. Peña considered him likely Human, although this wasn't firmly established in canon. Evil Never Dies was not published for several years; in the interim, Peña briefly mentioned Millennial in The Dark Forces Saga, released on the Wizards of the Coast web site in June 2005, marking the character's first canonical appearance. Evil Never Dies was subsequently released on StarWars.com Hyperspace one year later, expanding Millennial's backstory as established in The Dark Forces Saga.
With his previous Darth creation, Darth Ruin, Peña followed George Lucas's pattern of short Sith names, such as Darth Bane and Darth Maul. However, with Millennial, he opted for a longer name, similar to Lucas's Darth Sidious and Darth Plagueis. Millennial's religious nature led Peña to incorporate the concept of infinity into his name. He based it on "millennium," meaning a thousand years, as one thousand is the Arabic symbol for infinity, similar to the Western ∞ symbol and the Chinese culture's 萬物. The number one thousand also appears in several prominent Star Wars works, such as A New Hope, The Phantom Menace, and Tom Veitch's Star Wars: Dark Empire, influencing Peña's choice. Additionally, as Millennial lived around the time the Sith became extinct, Peña views his name as a self-fulfilling prophecy, as the Sith remained extinct for a millennium.
Millennial was later referenced in Ryder Windham's Jedi vs. Sith: The Essential Guide to the Force, Matthew Grau's Behind the Threat: The Sith, Part 1: Portrayal, and The Complete Star Wars Encyclopedia, by Daniel Wallace, Pablo Hidalgo, Stephen J. Sansweet, and Bob Vitas. In The Complete Star Wars Encyclopedia, Millennial's name is misspelled as "Darth Millenial." He also received his first official depiction in that work, portraying him as Human, thereby canonizing Peña's earlier comments about his likely species.