Mechanus

Also known as — (by Planewalkers) Clockwork Universe, Gear Plane, Mechanical Paradise, Plane of Ultimate Law; (by Primes) Nirvana

Welcome to the Machine

Mechanus. The very name draws a picture, using set square and protractor, of the Plane of Ultimate Law. A more rational and ordered place you’ll not find, but unless you can tumble to the logic behind it, the plane can be even more unfathomable than the chaotic soup of Limbo.

The perfect synthesis of world and machine, the plane of Mechanus does not have layers per se, but instead is constructed from an infinite number of gears and cogs, in turn connected by an ever-turning array of crankshafts, axles and rotors. Where the machine is kept oiled and greased it runs smooth and quiet, with only the gentle creak of metal rubbing against metal and the pungent smell of mechanical lubricant to remind a cutter he’s anywhere odd. Oh, and the view–even a hardened planewalker draws a sharp breath when they first clap eyes on Mechanus.

Where the caretakers of the machine are less vigilant, nearer the edges of Mechanus (as much as any infinite area can have edges) the grinding intensified, and can be almost unbearably shrill. It’s said that these parts of Mechanus are haunted by unquiet gear spirits, or Mathematicians driven barmy by the manyfold paradoxes of the plane.

A traveller must remember, of course, that Mechanus is far more three-dimensional than many planes. Gears and cogs can be orientated at any angle, but are usually all either horizontal or perpendicular to each other (the occasional cog can be found at other angles but these usually have complex connection mechanisms to ensure the motion of the plane is transmitted). Unlike many more “prime-like” Outer Planes, where most of the realms and burgs are found on the surface, there are burgs on Mechanus not only next to one another but stacked above and below, and at right angles. Some large cities can spill over several adjoining cogs, and the rotating bridges that engineers have made to cope with this are a sight to behold!

A number of useful facts about the plane are detailed below, but above all, a visitor should be warned to find out as much about the local laws as they can and stick to them rigidly. On Mechanus, Crime Doesn’t Pay.

“The sentence should be light.
All I did was walk on the wrong side of the street.”
— The (late) mage Fiwex

Physical Conditions of Mechanus

THE SKY — Mechanus doesn’t have a sky, as such, because the cogs and gears are endless in all directions. Mechanical locations can be found “above” or “below” as well, which makes mapping the place a sodding sight more difficult. The atmosphere of the plane is breathable for any creature—a fact that surprises many travellers. Water-breathing creatures can exist quite happily out of water (assuming they have the correct limbs to move around, that is), although most feel terribly uncomfortable with the idea and seek to return to water as quickly as possible. The air varies from fresh and crisp in the regions where the cogs are well-spaced, to smoggy and oily or polluted and grimy in the depths of the machine.

THE GROUND—Although it’s mostly cog and gear, the whole plane’s not metal. Much of the hard-wearing framework of Mechanus is steel, iron, or tungsten, but many cogs have soil and vegetation growing atop them. Sure, the trees and flowers are organised in neat rows of ascending height, similar colour and species, but that’s what passes for Natural on this perfect plane. Some cogs are actually made of stone, usually a hard granite or millstone grit, but planewalkers report cogs made from wood, slate, chalk, flint (watch out for the sparks!), glassteel, and even (allegedly) ice!

THE LIGHT—Mechanus is lit by an ambient glow that radiates from the space between the gears. Some cogs have glowing mosses, pools of lava, continual light spells or burning flames which cast additional shadows, but otherwise the plane is equally light all over. The glow fluctuates regularly across the whole plane, but never to be particularly bright or dark. ‘Days’ last exactly twelve hours, and ‘nights’ the same, but lighting conditions vary between an overcast day on Arborea (or a bright one in Sigil!) and dusky twilight.

THE LOCALS—Even a clueless prime knows Mechanus is the home of the modrons, the clockwork creatures who’ve made themselves responsible for cleaning and maintaining the delicate structure of the plane. Of course, the Fraternity of Order is drawn to the plane like a moth to dancing lights, but there’s a local sect called the Mathematicians too. The humanoid axiomites may be rare, but their history is closely entwined with that of the other races. Their offspring, the Inevitables, are mighty enforcers of societal law on Mechanus and beyond. Fewer cutters know of the other locals; the gear spirit petitioners who protect the machinery with a dryad’s fanaticism, or the moigno, mathematical extrapolations come alive. The most mysterious of all are the Aeons, weird creatures that protect the physical laws of the multiverse itself, who may or may not be emanations of the plane itself. Many sages have studied the ecology of Mechanus, but few can admit to understand the intricacies of the highly complex system. While everything that occurs on the plane is theoretically predictable, in practise there are so many variables that creating a working theory becomes humanly impossible. Of course, creatures like the moigno are rather more than mere humans, and many of them try to achieve just this…

THE LANGUAGE—Curiously enough, all spoken languages can be understood on Mechanus by all cutters. No matter how stupid a basher is, as long as they can talk, they can communicate with any other berk on Mechanus. Unfortunately, this savvy does not extend to the written word, so a basher hoping to use Mechanus’ linguistical gift to read an obscure piece of text will have to do it the old-fashioned way, an ask a graybeard.

THE LAWS—On the plane of Ultimate Law, a cutter had better watch their step. As any cross-trader can tell you, there’s nothing stricter than Mechanical law-enforcement, be they Guvner, inevitable or just local planar burg dwellers. A thief on this plane had better be good, or have a quick getaway plan, because once caught, there ain’t a court in the land that can be fast-talked. However, canny knights of the post have been able to fool Mechanical juries by invoking obscure laws and technicalities. It’s a difficult game to play, for nobody understands Law better than these folks, but apparently it’s possible. Fail and you’re dead, however.

Locations of Mechanus

Axis (city of the axiomites)†
Centre, the (capital of the formian empire on Mechanus)
- Manual of the Planes [3e] p128-129
Circular Unity (independent burg)‡
Cog that Doesn’t Spin, the (site)‡
Convergence, the (independent burg)‡
Dark Cogs (site)‡
Delon-Estin-Oti (independent burg)
- Manual of the Planes [3e] p129-130; Planes of Law [2e] Mechanus p16-18
Disc of Day and Night, the (realm of Ahau Kin)‡
Doomcourt (realm of Hoar)
Dying Light (former realm of Utu; now abandoned)‡
Everwatch (realm of Helm and Mystra)
- On Hallowed Ground [2e] p47,181; Planes of Law [2e] Mechanus p10; Player’s Guide p26; Planescape Campaign Setting [2e] DM’s Guide p61
Focus of Energy (realm of Rudra)
- On Hallowed Ground [2e] p156-157,179
Fortress of Disciplined Enlightenment (Guvner citadel)
- Catalogues of Enlightenment
- Office of the Sub-Bursar
- Dragon Magazine #315 p36; #353 p52; Factol’s Manifesto [2e] p72; Manual of the Planes [3e] p130; Planar Handbook [3e] p166-167; Planes of Law [2e] Mechanus p18-20,30; Player’s Guide p26; Planescape Campaign Setting [2e] DM’s Guide p61; Planewalker’s Handbook [2e] p66
Fumetown (area, gate)‡
Garden of Practicality and the House of Teaching, the (realm of Itzamna and Ix Chel)‡
Gleaming Spire, the (realm of Avani)
- On Hallowed Ground [2e] p162,179
Great Library (site)
- Planescape Campaign Setting [2e] DM’s Guide p61
Halirand (independent burg)‡
Haven (independent burg)
- Planes of Law [2e] Mechanus p32; Player’s Guide p27; Planewalker’s Handbook [2e] p23
Humanoid Settlement #1347-b (independent burg)‡
Jade Palace (realm of Shang-ti)
- On Hallowed Ground [2e] p152,178; Planes of Law [2e] Mechanus p10; Planescape Campaign Setting [2e] DM’s Guide p61
Keep of the Eternal Sun (realm of Amaunator; abandoned)
- On Hallowed Ground [2e] p182
Labyrinthine Portal (planar pathway)
- Dungeon Magazine #144 p74,78; Great Modron March [2e] p123; Planes of Law [2e] Arcadia p31; Mechanus p5,12,16,26,28,30-31; Player’s Guide p7,27
Nemausus / Menausus (unstable region)
- Book of Exalted Deeds [3e] p181; Factol’s Manifesto [2e] p90,99; Manual of the Planes [3e] p132; Planes of Law [2e] Arcadia p4,12,18,25,30; Mechanus p9,15,22
Neumannus (site)
- Life Molds of Neumannus
- Manual of the Planes [3e] p129; Planar Handbook [3e] p179-180
Mictlan (realm of the Aztec pantheon)‡
Music of the Gears (independent burg)‡
Mycelia (realm of Psilofyr)
- Palace of Psilofyr (site)
- On Hallowed Ground [2e] p176; Planes of law [2e] Mechanus 10-11,20-21
Mythenosca (myconid burg)
- Tales from the Infinite Staircase [2e] p19
Path of Law, the (realm of Pholtus)
- On Hallowed Ground [2e] p180
Plurality (independent burg)‡
Radian (headquarter burg of the Mathematicians sect) ‡
- Axle of Pi (site) ‡
- Labyrinthine Portal (planar pathway terminus) ‡
- Library of Numbers (site) ‡
- Set Square (site) ‡
Regulus (modron realm)
- Central Office for the Punishment of Offenders (site)
- Central Office of Processing and Requests (site)
- Great Modron Cathedral (site)
- Great Orrery(site)
- Primus’ Tower (realm of Primus)
- Dragon Magazine #341 p72; #354 p35-36,38,40-41,48-49; Great Modron March p12,123; Manual of the Planes [3e] p129; On Hallowed Ground [2e] p51,152; Planes of Law [2e] Mechanus p5,7,13,23-30; Player’s Guide p26-27; Planescape Campaign Setting [2e] DM’s Guide p61; Planewalker’s Handbook [2e] p23
Right to Rule (headquarter burg of the Legislate sect)‡
River Hister (planar pathway)‡
Sanctuary (hidden realm of the Keepers)‡
Sector 112 (site)
- Planes of Law [2e] Mechanus p26-27 (adventure set on cog in Sector 112)
Shaking Land, the (realm of Nai No Kami)
- On Hallowed Ground [2e] p179
Spiral Tower (site)‡
Stannia (independent burg)‡
Vigilant Eye, the (realm of Varuna)
- On Hallowed Ground [2e] p179
Waterwheel, the (realm of Enki; abandoned)
- Oh Hallowed Ground [2e] p182
Way, the (realm of Anu)
- On Hallowed Ground [2e] p64,172; Planescape Campaign Setting [2e] DM’s Guide p61; Planewalker’s Handbook [2e] p39
Wheel of Time, the (realm of Lendor)
- On Hallowed Ground [2e] p180
Yamasadena (realm of Yama)
- Vaitarani (river)
- On Hallowed Ground [2e] p157,179

Powers of Mechanus

Ahau Kin (Maya power of the sun)‡
Amaunator (power of the sun, rulership; dead)
- Guide to the Astral Plane [2e] p38; On Hallowed Ground [2e] p182
Anu (El, An) (Babylonian power of the sky, pantheon leader)
- Dragon Magazine #16 p4,6; #329 p36-37; Dungeon Magazine #148 p66; On Hallowed Ground [2e] p63-65,172; Planescape Campaign Setting [2e] DM’s Guide p61
Avani (Cerilian power of the Sun)
- On Hallowed Ground [2e] p47,162,179
Aztec pantheon‡
Enki (Ea) (Sumerian power of water) (dead)
- Dragon Magazine #16 p4; #329 p36-38; Factol’s Manifesto [2e] p123; Guide to the Astral Plane [2e] p38; On Hallowed Ground [2e] p43,62-63,65,182; Uncaged [2e] p112
Hoar (Assuran) (Faerûnian power of revenge and retribution)
- Dragon #357 p87; #358 p70-71
Helm (Faerûnian power of guardians and protection)
- On Hallowed Ground [2e] p47,181; Planes of Law [2e] Mechanus p10; Player’s Guide p26; Planescape Campaign Setting [2e] DM’s Guide 61
Itzamna (Maya power of writing and teaching)‡
Ix Chel (Maya power of childbirth and medicine)‡
Lendor (Oerdian power of time)
- Dragon Magazine #350 p28; On Hallowed Ground [2e] p180
Mystra (Faerunian power of magic)
- Dead Gods [2e] p122; For Duty & Deity [2e] p27,33; On Hallowed Ground [2e] p88,167-171,181; Planes of Law [2e] Mechanus p10-11; Player’s Guide p26; Planes of Conflict [2e] Liber Benevolentiae p50; Planescape Campaign Setting [2e] DM’s Guide 61
Nai No Kami (Japanese power of earthquakes)
- On Hallowed Ground [2e] p159,179; Planes of Law [2e] Mechanus p10; Player’s Guide p26
Pholtus (Oerdian power of light and law)
- Dragon Magazine #346 p22-23,26; #350 p20; #354 p26,28; #358 p30-32; On Hallowed Ground [2e] p47,180
Primus (the primal modron)
- Dead Gods [2e] p8-9,36-37,124; Dragon Magazine #341 p71-74; #354 p35-37,41; Dungeon Magazine #144 p74,76-79,82; Great Modron March p11-13,123; Hellbound [2e] Dark of the War p33,69; In the Cage [2e] p30; On Hallowed Ground [2e] p42,51,152; Planes of Law [2e] Mechanus p5,10,13,23-24,28; Player’s Guide p26; Player’s Primer to the Outlands [2e] p8; Planescape Campaign Setting [2e] DM’s Guide p61; Monstrous Supplement p16-18,22; Sigil & Beyond p29; Uncaged [2e] p19
Psilofyr (myconid power of community and healing)
- On Hallowed Ground [2e] p176; Planes of Law [2e] Mechanus p10-11,20-21; Player’s Guide p26
Rudra (Aditya / Vedic power of storms and disease)
- Planescape Monstrous Compendium [2e] p66-67; On Hallowed Ground [2e] p154,156-157,179; Planes of Law [2e] Mechanus p10; Player’s Guide p26; Planescape Campaign Setting [2e] DM’s Guide p61
Shang-ti (Chinese power of nobles, pantheon leader)
- In the Cage [2e] p30; On Hallowed Ground [2e] p152,178; Planes of Chaos [2e] Book of Chaos p39; Planes of Law [2e] Mechanus p9-10; Player’s Guide p26; Planescape Campaign Setting [2e] DM’s Guide p61; Sigil & Beyond p44,91
Varuna (Vedic power of cosmic order and dharma)
- On Hallowed Ground [2e] p47,154-155,157,179; Planes of Law [2e] Mechanus p10; Player’s Guide p26; Planescape Campaign Setting [2e] DM’s Guide p61
Yama (Aditya / Vedic power of judgement of the dead)
- On Hallowed Ground [2e] p47,154,179; Planes of Law [2e] Mechanus p10; Player’s Guide p26; Planes of Conflict [2e] Liber Benevolentiae p30; Planescape Campaign Setting [2e] DM’s Guide p61

Empires of Mechanus

Axiomites
- Inevitables
- Moigno
Formians
Modrons

Pathways of Mechanus

Labyrinthine Portal — being a Complex Pathway Touching All Cogs of Mechanus
Mictlan — being a One-Way Aztec Pathway
River Hister — which was Recently Diverted
Via Romana — which Leads from Upper to the Lower Planes

Philosophies of Mechanus

Cant of Mechanus — speak like a Guvner
Circle, the (the myconid kings of Mycelia)
- Planes of Law [2e] Mechanus p21
Fraternity of Order (faction)
Legislate, the (sect)‡
Mathematicians, the (sect)
- Factol’s Manifesto [2e] p77; Planes of Law [2e] Mechanus p5,12; Uncaged [2e] p123
Planar Architects’ Guild‡
Rustcatchers’ Guild‡
Tamers of Chaos (sect)‡

Law-Abiding Cutters of Mechanus

Black Pete (planar githzerai magus [he/him] / Fraternity of Order / LN) — Regulus
Bluestreak (decaton modron [it/its] / LN)
Britin, Jarua (planar human [she/her] / Fraternity of Order / LN) — Delon-Estin Oti
Clarakis, Judge Naracyl — Fortress of Disciplined Enlightenment
Decayer, Cybin (myconid cleric proxy of Psilofyr [they/them] / LN) — Mycelia
Garabutos, Lady Nancias (planar human female wizard [she/her] Fraternity of Order / LN) — Fortress of Disciplined Enlightenment
Hexadrone 5 (1st Sector) Planes of Law [2e] Mechanus p13
Hsirani (human wizard proxy of Azuth [he/him] / LN) — Nemausus
Krenurum (orc fighter proxy of Meriadar [she/her] / LN) — Nemausus
Laretua Quinton (planar human diviner [she/her] / Prime Digit of the Mathematicians / LN) ‡
Lithinal Endivar (petitioner half-elf [he/him] / LG) Nemausus
Monodrone 439 (9th Sector) Planes of Law [2e] Mechanus p22
Quotidia (planar tiefling wizard [she/her] / Mathematicians / LN)
Septiembre (planar septon modron [it/its] / LN) — Regulus
Sprocket 7 (leader of the Rustcatchers’ Guild) Fumetown ‡
Talandra the Bright (human fighter proxy of Yama [she/her] / LN)
Tenmar the Undying (human cleric proxy of Anu [he/him] / Fraternity of Order / LN)
More details to follow!

Source: Jon Winter-Holt, mimir.net

Canonical References: See also the excellent Planes of Law boxed set for more details on Mechanus. Canonwatch: Entries are from D&D canon unless otherwise marked, although when the canon is sparse I’ve got creative with the details; † adapted from a 3rd party publication; ‡ homebrew.