It is the plane of ultimate law.

It is where premeditated plans are born.

It is the gear works for the multiverse.

Mechanus is where perfectly regimented order reigns supreme. It consists of equal measures of light and dark, and equal proportions of heat and cold. It is as predictable as the drip of a water clock and as obvious as a tree in a field. On Mechanus all law is reflected in a single infinite realm of clockwork gears, all interlocked, all turning according to their own measure. The cogs seem to be engaged in a calculation so vast that no deity knows its purpose, except that it is somehow a function of law. At first glance Mechanus seems as straightforward as anything on the Outer Planes. However, subtleties lurk just below the surface. Every kind of law can be found in the Clockwork Nirvana of Mechanus, from simple maxims to devilishly twisted rules of decorum. But for the most part, Mechanus contains no passion, illusion, or pain. When all consciousness is completely subsumed into the whole, perfection follows.


Mechanus has the following traits.

 Objective Directional Gravity: The strength of gravity is the same as on the Material Plane but the direction is oriented to the face of each rotating cog. Walking between cogs can be dizzying for newcomersand dangerous if a traveler falls between the cogs.

 Normal Time.

 Infinite Size: Each cog is finite, though even the smaller ones are as big as a typical island. The void the gears hang in is infinite.

 Divinely Morphic: Lesser deities can alter Mechanus with a thought; ordinary creatures require spells and physical effort to do so.

 No Elemental or Energy Traits.

 Strongly Law-Aligned: Nonlawful characters on Mechanus suffer a 2 penalty on all Charisma-, Wisdom-, and Intelligence-based checks.

 Normal Magic.


Free-standing portals from elsewhere usually connect at the center of any given cog. Some portals lead to other Outer Planes, Inner Planes, or even the Astral Plane or Ethereal Plane. 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.


The inhabitants of Mechanus make their homes on the cogs that turn in the void. The gear faces are normally devoid of vegetation and native wildlife, although colonists from other planes, including the Material Plane, the Nine Hells, and Celestia, transform many faces into elaborate hedge mazes, parks, or nature reserves. The most prevalent creatures on Mechanus are not truly living creatures at allthey're constructs. As a group they are called inevitables, and they exist to enforce the natural laws of the universe. The three widely recognized types of inevitables are kolyaruts (fugitive-hunters), maruts (foes of those who cheat death), and zelekhuts (enforcers of contracts). Each type of inevitable relentlessly finds and punishes those who have committed such transgressions. Expansionist formians have hives throughout Mechanus. These antlike centaurs seek to colonize all they see and incorporate all living things into their hives as workers, serving the law of their queens. Other clockwork creatures, apart from inevitables, also call Mechanus home, though they have as little as possible to do with other races.

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. Mechanus petitioners have the following special petitioner qualities:

Additional Immunities: Fire, cold.

Resistances: None.

Other Special Qualities: None.


Movement in the Clockwork Nirvana of Mechanus is much like movement on the Material Plane. Walking between turning cogs seems daunting to the uninitiated, requiring a Balance check (DC 10). This is a relatively easy check, but failure by 5 or more means a fall between the cogs, which deals 20d6 points of damage each round. It takes a climb check (DC 20) to emerge from the teeth of the cogs. Travelers can move between the cogs by flying or teleporting through the void, of course.

mechanus map


Mechanus is a single infinite plane without defined layers. The void is filled with gargantuan interlocking wheels, like the internal cogs of an ornately carved clock. Some connect at right angles, and others connect along a single plane. The wheels, also called cogs, are composed of stone, earth, and metal ores, as if a deity carved them from the mantle of the Material Plane. Many of the cogs are more than a thousand miles across, and they turn so slowly that their rotation is imperceptible. Yet turn they do, as witnessed by much smaller island-sized cogs that interlock with the much larger wheels. These smaller cogs seem to turn at an almost dizzying pace, although inhabitants feel no centripetal force once on the surface of a small cog. The objective directional gravity means that inhabitants won't be spun off the edge of a cog unless they're standing within 10 feet of the rim. Vision is normal on Mechanus. The plane is lit by a white, all-encompassing light springing from the very void for 12 hours, and is dark for 12 hours. Hearing is also normal, though the bass rumbling of cog turning on cog is sometimes audible near the edge of a face. Formian Hive Cogs The formians build fabulous hive-cities on both faces of a cog they colonize. Each colonized hive-cog holds thousands of workers, warriors, and taskmasters, as well as several dozen or more myrmarchs. However, each cog has only one queen, whose commands are absolute law on the hive cog. Other queens rule other cogs. Usually two queens cooperate with each other, unless each wishes to colonize the same cog, in which case the law of the formians demands warfare. If a queen chooses to colonize a cog by sending a contingent guarding a precious queen larva, she is not swayed if other creatures already reside there. After all, what are warriors for, if not to make a cog ready for formian colonization? Luckily, the birth of a fledgling queen from the many eggs laid happens only once every one hundred to one thousand years. Otherwise the formians would hold much more of Mechanus than they already do. The Center: Travelers who move through the void of Mechanus in the direction from which the formians originate find that the formian-colonized cogs become more and more frequent until noncolonized cogs are nonexistentmillions of cogs, or perhaps more, all crawling with formians. At the heart of the formian realm, surrounded in all directions by colonized cogs, lies the centermost cog where the Scion Queen Mother resides. Formian myrmarchs believe that the Scion Queen Mother's cog, which has a diameter of at least three thousand miles, is the center cog for all Mechanus and imparts movement to all the other cogs of the plane. Whether true or simply a belief, the grandeur of the two-sided hive-city that covers the surface area of the cog is godly in its splendor. The Scion Queen Mother herself claims the power of an intermediate deity, though this claim is difficult to scrutinize. Thirty-three gargantuan formian queens of maximum advancement attend the Scion Queen Mother at all times, and even her escorts are still dwarfed by the Scion Queen Mother's bulk.


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.


Clockwork creatures reside on Mechanus in a realm called Regulus and seem well suited to it. These alien beings, called modrons, look and act like constructs but breathe and eat like the outsiders they are. The modrons control sixty-four cogs, and this number never varies. In truth, modrons outwardly hold many traits in common with inevitables, but modrons are not concerned with maintaining their own ordered society, not punishing other creatures for broken laws. The formians have yet to test the modrons' strength, although such a conflict is likely as the formians continue to expand.

Other Sites on Mechanus

If the void of Mechanus is infinite, then the cogs must also be numberless. The disks that make up the plane all interlock, so there is no part of Mechanus that is not connected to some other part. Technically, there is no place a traveler can't go if he is determined and long-lived enough. For all its lawful conformity, Mechanus holds countless sites of interest.

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.

Mechanus Encounters

Use Table 77: Hellish Encounters or Table 78: Heavenly Encounters (alternate between them) for random encounters on Mechanus.