Type Outer Plane
Celestial Plane
Native(s) Mordons, inevitables, and mercane
Alignment Trait Mildly law-aligned and mildly good-aligned
Physical Traits:
Gravity Objective Directional Gravity(Normal): The strength of gravity is the same as on the Prime Plane but the direction is oriented to the face of each rotating cog. Walking between cogs can be dizzying for newcomers—and dangerous if a traveler falls between the cogs.
Time Normal
Shape & Size immeasurable size
Morphic Trait Alterable morphic (each divine realm is divinely morphic)
Faith Trait
Elemental & Energy Traits None
Magic Trait

Mechanus is the plane of ultimate law and order (neutral or chaotic creatures take -2 penalty on Charisma, Intelligence and Wisdom-based checks), where the souls of people of lawful neutral alignment go after death. Mechanus operates on a strict schedule where every action is planned, measured and controlled perfectly. It is home to the construct-like geometric modrons, the law-enforcing inevitables and the regimented giant ants called formians.


Mechanus consists of a single infinite plane, there are no constituent layers. Mechanus shares its borders with the neighboring planes of Arcadia and Acheron. Travel is possible between Mechanus and these planes at certain locations. Free-standing portals from elsewhere usually connect at the center of any given cog. Some portals even lead to other cog faces. Portals on Mechanus appear as light green coglike circles, slowly turning. A green portal appears regularly once per revolution of the cog it resides upon, though some portals appear according to the interaction of several cogs (and which ones are not always readily apparent). Once it appears, a given portal usually remains open for at least 1 hour and possibly as long as 24 hours.

Throughout Mechanus exists a series of interlocking cogs that float in space, intersecting at all angles and directions. Many of the cogs are gigantic, stretching many miles across and turn so slowly that the rotation is undetectable. Smaller cogs can move at much higher speeds, but no acceleration is experienced, except at the very edges. Usually smaller cogs bunch up with larger ones; these are called knots. The gears are fiercely guarded by gear spirits that reside within them. The gravitational force is oriented towards the face of each individual cog, making intercog travel a disconcerting experience for the uninitiated.

Magic in Mechanus

Only lawful creatures can be summoned, but they will be obedient. They will twist the instructions of chaotic summoners. If the alignment is identical, the creature will do its best to serve well. Chaotics cannot divine. Illusions do not even manifest. Necromancy requires 1 hp for a first-level spell, and 4*(level-1) for others. Wild magic fails. Elemental magic requires a bit of the element native to the plane, and there is good earth and water only in Nemausus. Spell keys might be able to allow a chaotic to use divinations, but keys to overcome other limitations of the plane seem unlikely.

Wizardly spell keys are one-twelfth of a cog, colored appropriately and marked with the sigil of a spell school. If twelve such keys, one for each school, are joined and absorbed by a wizard, they will never be lost, but all spells cast off the plane will be at half effect. Or, for necromancy, a bit of a modron's body and a prayer in Chinese. Power keys for clergy are little gears, and they return to sect headquarters, along with the user, at the end of the day. Lawful owners will always get them back, perhaps with the key renewed. Woe to anyone who has stolen a power key!

  • -1 on all intelligence, wisdom, and charisma checks for all non-lawful, non-chaotic creatures
  • -2 on all intelligence, wisdom, and charisma checks for all chaotic creatures
  • Good-based spells (non-chaotic) are unaffected.
  • Evil-based spells (non-chaotic) are unaffected.
  • Law-based spells work as if caster were 4 levels higher.
  • Chaos-based spells simply fail.


Regulus is the home of the Modrons. Their strict hierarchy originates from Primus. Regulus consists of a total of sixty-four cogs, a number that never varies. It is divided into four quarters of sixteen cogs, each ruled by a Secundus. Each quarter is in turn split into four regions, of four cogs, each ruled by a Quarton. Finally, the regions are further subdivided into four sectors, of a single cog each, ruled by an Octon.

  • The Center

At the center of the Formian realm lies a central cog more than three-thousand miles across, where the Scion Queen Mother, leader of the Formians resides. The central cog supposedly imparts the movement to all other cogs in Mechanus.

Divine Domains

  • Everwatch: Helm's realm
  • Mycelia: the myconid deity Psilofyr's realm
  • Anu's Way: Anu's Way is ruled by Anu. Here exists a single huge disc, upon which his palace rests. An enormous gear of orderly lines and clay brick buldings. He is served by einheriar called the soldiers of Anu - they have copper skin, yellow eyes without pupils, and no apparent gender. All have the same memory and knowledge, making them more like modrons than people. Anu rules from the center of his realm, upon a great raised throne. At his side is the goddess Anutu, his sister and wife.
  • The Jade Palace The Jade Palace is home to Shang-ti, the Celestial Emperor. His palace is the focal point of the Celestial Bureaucracy, which also supervises the Chinese pantheon. The Great Library can be found here. The Jade Palace is home to Shang-ti, the Celestial Emperor. His palace is the focal point of the Celestial Bureaucracy, which also supervises the Chinese pantheon. The Jade Palace is located far from Regulus and the interference of the modrons (though Shang-ti counts Primus as an ally). Shang-ti lives in the center of his disk-like domain with his family, his court, his messengers, and his ministers. The door to his audience room is kept by Wang, the transcendental bureaucrat. Foo dogs and foo lions patrol the grounds of the Jade Palace, which is planted with ever-ripe peaches of immortality similar to those tended by Shou Hsing.

The library of Shang-ti contains all the books and knowledge lost on those Prime Material worlds that recognize his authority. His librarians are tall, faceless giants in gray cloaks, who visit those places where disaster is about to hit and rescue knowledge from destruction.

Shang-ti's disk interlocks with the marine realm of Shan-Hai Ching.

  • Neumannus: Possibly named after mathematician John von Neumann, it is a series of mysterious self-sustaining factories that produce inevitables. It is managed and presided by the Hub of Elders, who seeks out any non-lawful activity (broken contracts, etc.) that needs to be corrected. Inevitables are designed, constructed, and assigned tasks to uphold various laws. It is unknown who created the first inevitable; even inevitables claim ignorance as to their own origin. But once created, the constructs soon learned the trick of replicating themselves. Neumannus is one such “factory” inhabiting a small cog. It is a place devoid of regular life, though it is crawling with inevitables at all times. Tall smokestacks cover both sides of the cog and constantly belch sooty clouds from the fires raging in forges and furnaces. Inside, chamber after chamber is given over to crystal molds of dizzying variety. Liquid metal is cooled, shaped, and tempered in these molds by special constructs. Finished pieces are assembled and animated in arcane baths of oillike consistency. After a brief shakedown period, the newly constructed inevitable is sent out onto the Great Wheel with its first task. Tasks are magically encoded on the construct in glowing runes handed down by the Hub of Elders (each factory has its own hub). The elders are several hundred special inevitables that spend their time peering through the cosmos looking for broken laws for which amends must be paid. Sometimes, inevitables bow to other noted authorities of law in the Outer Planes, doing their bidding for a short period.
  • Delon-Estin Oti: This perfectly symmetrical town is located on a far larger cog, taking up only a small part of it. Delon-Estin Oti has twenty bordering walls, with one gate on each side. Farmers till plots of fruits and vegetables and nurture animals just inside the gates. Seen from above, the town looks like a spiderweb, with concentric roads radiating from the hub, a great open space covered with grass, and a single ring of trees at the very center. The town is one of peace and tranquility, a place where everything is so ordered and habitual that citizens anticipate the course of time and flow of conversation, interrupting visitors who don't know what the future holds. Those who seek perfect equality and freedom from the lower (and higher) passions make their homes here. The population is a mixed collection of every race on the Great Wheel, but all are equal and there is no ruler. Many petitioners also reside within and around Delon-Estin Oti, happy to work the agricultural plots. The town has a reputation as a place where seers are born and where fortune-tellers gravitate, so visitors hoping to discover their fate are common.
  • Fortress of Disciplined Enlightenment: This structure sits on its own cog, and its spires and towers rise high into the void of Mechanus. The fortress is two miles in diameter, and some of its spires reach twice that height. Inevitables enforcing the “don't trespass” law patrol the parapets, keeping a vigilant eye out for fiendish infiltrators or colonizing formians. A group of mortals from the Material Plane called the Fraternity of Order are the masters of the fortress. The members of the Fraternity of Order believe that if they can but tease forth every law of the cosmos, they will have the power of the deities. To that end, they built this stronghold on the plane of ultimate law. A horde of clerks, functionaries, legal aides, translators, mathematicians, philosophers, and bureaucrats staff the Fortress of Disciplined Enlightenment. Most belong to the Fraternity of Order, though sometimes visitors are granted access to study at the vaunted libraries of the Fortress. The libraries extend through hundreds of rooms and hold tomes of legal volumes from all over the Great Wheel.
  • The Eternal Moon Character. There is no truth without understanding; there is no understanding without rules; there are no rules without math, as

there is nothing in the multiverse which can not be calculated. Nothing in this existence is without a meaning, and to find the truth of the multiverse, everything must be analyzed - and for that, everything must exist. Leguleius is the God of Rules and Numbers. He longs to understand all of existence, and he wants to share his knowledge with the multiverse. Residing in the mysterious City of Moonlight, which only his most powerful proxies ever get to see, Leguleius constantly creates new experiments to grant understanding. Rare among the powers of Mechanus, this deity does not consider any belief wrong or right until perfectly proven. Even more unusual, Leguleius accepts priests and proxies of all alignments - although nearly all of them are lawful neutral.

The realm of Leguleius is shaped like the disc of a full moon. Three large continents provide space for countless petitioners, and the silvery oceans provide a comforting light for the whole realm. There is no day or night here, only past, present and future. Many different calendars have been created to measure time; the most commonly used is the Moonlight Calendar, which is based on changes in the colour and strength of light that are so subtle only the petitioners of Leguleius can sense them. The continents are covered with vast cities, most of them providing shelter for hundreds of thousands of people. Everyone is welcome here, as long as he/she/it keeps to the existing laws. In general, as far as one keeps to normal civilized standards and doesn't harm or anger anyone, this realm is a nice place to live. Besides petitioners, countless other beings (most of lawful alignment) inhabit these cities. Only few modrons are seen here - Leguleius is not at war with Primus, but both don't get along with each other. A bit more common are baatezu and aasimon, and they often meet here if they have to do some negotiations.

Beyond the cities, a harmless and calm "wildlife" is found. Fine roads provide a good way, and merchants constantly use them without danger of being attacked by anyone or anything. Since there are strict rules for prices, merchants never get truly rich. The oceans of The Eternal Moon are inhabited by few animals, most common being small fish. Lizard men cities in the coastal regions are quite common, and a few non-dangerous swamps can be found. The most interesting about this realm are the inhabitants, for sure.

Petitioners usually have a high intelligence, and few places with so many sages can be found. The best about this, they provide their knowledge for extremely low prices - and sometimes even for free. Minor questions are usually answered without a fee. One topic still belongs to the most favourite ones in this realm: The banishment of a whole pantheon of the world of Sikris. Leguleius belonged to this pantheon, where he was an intermediate god. Those petitioners who lived their mortal lives on Sikris have many theories on what exactly happened two millennia ago, but the only known facts are that a godly war was about to erupt, and a few gods of the pantheon tried to take over the rulership by a cunningly evil plan. This plan failed (rumors say that Leguleius had a hand in this failure), and something led to said banishment of the whole pantheon. Only a few gods survived this catastrophe, among them Leguleius and his greatest allies.

Currently, Leguleius does not seem to be in contact with the surviving deities of Sikris. Instead, he concentrates very much on his new "home", Fumarenya, where he has taken over the task of supervising the pact between Litat and Iubar. Leguleius has set up a special army of powerful proxies to interfere if one of the other gods of Fumarenya acts in a way not allowed by the pact. This happened quite often in the first millennium, but nowadays the aggression between Litat and Iubar mainly keep to a very subtle acting. Still, Leguleius keeps his eyes open - and if the evil Litat or the good Iubar break the contract, he fulfills his task and punishes the god accordingly.

Although an "invader" in the Fumarenyan pantheon and less powerful than the world's original gods, many people think that the pact granting Leguleius the power to punish the other gods will, in the long run, make him the ruling power of Fumarenya. Others say that his presence in Fumarenya actually changed the deity himself, as Leguleius' influence in regions of other than lawful neutral alignment grows larger and larger. There is an order of lizard men assassins serving him, and since a few centuries Leguleius has granted paladinhood to a few mortals. Some sages belief that the God of Rules and Numbers will split into several deities in a few millennia if this development doesn't change.

Special Conditions: It is possible to actually reach the borders of The Eternal Moon. The disc connects to the gears of Mechanus seemingly everywhere (or maybe only those places which connect to other gears are accessable), and by leaving The Eternal Moon, one gets to either a "normal" gear or Mechanus, with modrons and all, or to the realm of a different power of Mechanus, e.g. the Jade Palace of Shang-Ti or the realm of Rudra (with whom Leguleius is more or less befriended). Different from other places in Mechanus, it is possible to cast illusions here. The flaws of illusions are always very apparent, so it is not possible to cheat anyone with them - but illusionists have found out that it is especially easy to create new illusion spells here, as the problems and mistakes in an illusion are so apparent here. Wild Magic is twisted in a different way: The spell is always changed into a random spell of the same level, but one that doesn't create any dangerous or upsetting situations.

Principal Nonplayer Characters: Due to the friendship/alliance between Rudra and Leguleius, the latter god is served by a number of Maruts. Each city is governed by a Lawful Neutral petitioner with Intelligence and Wisdom of at least 17, and guarded by a Marut. The most popular of these mayors is Harasha, who serves as Leguleius' high priestess in The Eternal Moon. Most residents think she is a chosen of Leguleius; others believe she is actually more than a "normal" petitioner, maybe a powerful proxy. Harasha (Pe(maybe Pr)/female human/Priest 18/LN) doesn't answer any questions about this topic - although she is otherwise a very friendly and open-hearted person, and acts as a sage and counsellor for everyone who asks for her help.

Services: Besides the many sages in this realm, The Eternal Moon provides shelter and civilization for those who adapt to a calm, but intellectual society. The few baatezu in this realm learn fast not to try luring anyone to making contracts with them, and they usually have some other mission here than corrupting or hunting someone. Due to the strict but fair laws, the merchants in The Eternal Moon tend to be very honest people - something found very rarely in the multiverse...

Mechanus Petitioners

The petitioners of Mechanus often adopt a stylized version of their mortal bodies. Despite the outward differences, all petitioners on Mechanus are alike in their frightening honesty and submersion of individuality. They are notoriously literal, and some take no instruction at all for fear of misinterpreting the speaker.



  • Coggles resemble the gears of Mechanus, but they are mobile, and modrons use them for transport.
  • Moignos are two-dimensional creatures made of mathematics, obsessed with finding the value of irrational numbers. They perform a variety of other useful calculations for the modrons.



  • Chaturani are living chess pieces.
  • Axial dragon
  • Flards are infinitely tall marble columns created by an extinct race to record all knowledge (Dragon #47).
  • Formians are a race of intelligent giant ant-centaurs obsessed with dominating everything in the name of order.
  • Gear spirits are pieces of living metal whose function is to tend to the gears of Mechanus and ensure their smooth operation. They are similar to nature spirits such as dryads, but take the forms of axles, padlocks, chains, and other tools. Most gears seem to have more than one gear spirit.
  • Inevitables are constructs tasked with enforcing justice and law.
  • Modrons are clockwork personifications of pure Law that take the form of various geometric shapes.
  • Paraii (singular: parai), also called visilights, are humanoids that seem to be made of porcelain, except for the ball of white light inside their hollow heads.
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