Primus

Primus, also known as The One and Prime and the Supreme Modron, was a Greater Power and the immortal ruler of Mechanus and the modrons. While it retained godlike power within its realm, Primus was not immortal and could be killed.

"Quote? You desire a quote? The One and the Prime does not give 'quotes'."

- Primus to a record keeper of the Fraternity of Order

Description
Primus appeared as a large being—sometimes in a form of an androgynous gold-skinned humanoid with a face of emotionless expression. While in Mechanus, its body remained half-submerged in an energy pool within the center of the Great Modron Cathedral. Primus' form was connected to the expansive interface network known as the Infinity Web. Primus' hands always remained unseen. Its right hand was obscured by vibrant, rainbow hued radiance, and the left was shrouded in black clouds.

The Supreme Modron retained much of its form after it was slain and reborn as a vestige. As Primus was no longer bound to the Infinity Web and its energy pool, its humanoid form manifested atop a floating platform of a bronze seal, intricately linked to cogs, gears, and other revolving machinery.

Personality
Primus was a manifestation of perfect logic and strict order. It was linked with the plane of Mechanus and they shared the same goals and actions. While some believed it only concerned itself with the plane's modrons, others believed Primus sought to extend perfect law and order throughout the entirety of the multiverse.

It absolutely detested the tanar'ri of the Abyss, and held similar, if not as intense, enmity for the baatezu of the Nine Hells.

Abilities
Primus was considered a greater deity in Mechanus. Its power over the modrons was absolute. Nearly all modrons obeyed the orders of Primus and carried out its plans, save for those that were disconnected from Primus' network and went 'rogue'.

Despite its immense power while in Mechanus, Primus was incapable of dispatching avatars to other planes of existence. It could however instantly transport any being it touched to either Arcadia or Acheron, by mere touch of its right or left hand respectively. Primus itself was entirely immune to magic.

While Primus held the powers of a god, it was not immortal and could still be killed. Whenever slain, the highest-ranking secundus modron was promoted to its position and became the new Primus.

Possessions
Primus had access to the Grand Orrery, an elaborate and complex device that calculated the changes between the heavenly bodies of space, the numerous planes of existence, and the infinite powers of the cosmos.

Activities
The One and Prime established the rules and laws that governed all of Mechanus and its inhabitants. Through its supervision of the modrons, Primus maintained near-perfect order within the plane. Primus could issue to each modron telepathic commands and perceive the plane through their eyes, by means of the Infinity Web. Primus was often subtle in its maneuvering, arranging for events that would cause its followers to take actions that were deemed most suitable.

Due to the fact many modrons died in the lower planes during their Great Modron Marches, Primus sought a solution to lessening their casualties as a result of the eternal Blood War.

Worshipers
While there were no known cults of Primus within Mechanus, it was worshiped as a deity by modrons. Primus was capable of creating new monodrones and could grant any modron divine powers.

As a vestige, Primus was capable of attracting binders, spellcasters that gained powers from powerful extra-planar beings.

The Prime Architect
According to chronicles maintained by the Fraternity of Order in Sigil, in an ancient time when even the Elemental Chaos was young known as the Age of Creation, the primordials made and unmade worlds as they willed, without pattern or permanency. Unique among them was a primordial known only as the Prime Architect. It looked beyond the veil of the Elemental Chaos, the very first being to do so, and had a vision of a perfectly ordered and harmonious reality it termed the Accordant Expanse. Inspired by it, the Prime Architect and four elemental lords it enlisted, as well as their archomentals, worked to bring order to the Elemental Chaos, creating the elements of air and earth, fire and water, as well as mixtures of these. The new symmetry and structure allowed worlds to persist and mortal life to exist.

But no sooner had the Prime Architect finished this great work and surveyed it than minute flaws began to appear, quickly growing and multiplying into flesh-like threads of corruption that writhed in blueish slime. Finally, these tendrils ensnared one world and swallowed it into their mass, where it was consumed by some immense worm-like thing—the entity later known as the Nine-Tongued Worm. Stirring from its shock and horror, the Prime Architect did battle with the worm in a desperate effort to stop it chewing a hole in the planes and crawling fully out of the Far Realm, the chaotic counterpart of the Accordant Expanse. While accounts of their titanic conflict were vague, the Prime Architect defeated the Devourer of Worlds, but only narrowly and at the cost of its own existence. Dying and unable to stabilize the Elemental Chaos, the Prime Architect drew on the Accordant Expanse, bathed in the energy of absolute order, and abandoned its flesh.

The One and Prime
Then the primordial was reborn as countless individual yet linked mechanical creatures—the modrons. The modrons assembled themselves into an army and swiftly advanced across the planes to seal all the breaches to the Far Realm, before they returned to the Accordant Expanse. There, they built the clockwork city of Mechanus, at the center of which they constructed a cathedral to the Prime Architect. After exactly 289 years, the four highest-ranking joined one another in a glittering pool of pure order and became Primus, a vestige of the Prime Architect with new life and purpose. Then, every 289 years, the modrons went on their Great Modron Marches across the planes, their purpose known only to Primus, surveying sites and occasionally closing, sealing, and collapsing planar portals and gates as they went.

At some point in existence, Primus created a massive stone crafted in complex geometry known as the Spawning Stone and imbued it with the essence of law itself. It then cast it into the plane of Limbo, believing it would cure its chaotic nature and establish some form of order. This act had an effect that was diametrically opposed to Primus' original intent: it led to the creation of the slaadi race. The Slaadi then proceeded to annihilate every modron outpost within all of Limbo.

Primus was said to have once adjudicated the trial of Asmodeus, when he was accused of horrific atrocities by the angels of Celestia. In the end, Primus did not find wholly in favor of either party. Rather he rebuked the celestial angels and ensured Asmodeus would always have to be bound to the force of law.

The One and Prime and its distinguished position among the modrons were known in the Realms since at least since. It was that year the plane of Mechanus was discovered by the Netherese archmage, Lady Polaris.

Primus was killed by Tenebrous—the dark vestige created after the death of Orcus—during the demon lord's quest for divinity. Tenebrous then temporarily took over its position as head of the modrons, and initiated an unscheduled Modron March in order to recover his lost Wand of Orcus.

While the role of Primus was replaced by one of its secundi, the mind of the previous Primus remained present in the multiverse in the form of a vestige.

Connections
Primus