modrons 5e guide

Modrons 5e Guide

Modrons, Meticulously Marching Mechanisms

Modrons are what happens when you let the IT Robotics nerd ascend to god-status. Crafted by the godlike Primus, Modrons act as the embodiment of Lawful Neutral on the classic DnD alignment scale. 

Where Lawful Good is reigned by Celestials and Lawful Evil is the domain of Devils, Modrons reign over Order. 

The perfection of clockwork is given form in their realm, but will I ever find out why the official art seems inclined to provide them with increasingly creepier smiles? 

In my hunt for the answer to that question, I found some fascinating lore on a species of mechanical wonder for those of you looking to spice up your Outer Planes Lore.

Let’s kick off our Modrons 5e guide and tinker with the Modrons.

Modrons, Orderly but Obnoxious

Modrons are the beacons of Law and Order. Unlike Celestials and Fiends, they embodied the neutrality of the Universal Order. Of course, they are still lawful about it rather than true neutral, but all Modrons know their place. 

They consider all other forms of law that do not follow their decree corrupt. To a Modron, the whim of Primus is the actual and perfect realization of law. They are described as having increasingly strange bodies, which, as they get promoted, evolve into more unsettling yet orderly geometric shapes. 

Monodrones, the simplest Modron capable of performing only a single task, will likely be the Modron you will face. The issue is they are typically found in a swarm led by more dangerous Modrons. Sometimes the absurdly powerful Hierarchs decide to direct the show. 

Really, you only have to worry once they get five or more sides.

  • All Modrons lack a sense of taste, but a rare few have a sense of smell. 
  • The more sides a Modron has, the more complex its structure becomes.
  • The more sides a Modron has, the higher their rank in Modron society.
  • Every 289 years, thousands of Modrons tour the seventeen Outer Planes in an event known as the Great Modron March. It is unknown why, exactly, they do this.
  • While exceptionally rare, rogue Modrons do exist. 
  • If a Modron of a higher rank dies, a lesser ranked Modron will evolve to take their place. 
  • Shockingly, this includes the godlike Primus. Replaced by a Secundus the moment he is slain.
  • There are concerns that Primus is actually an imprisoned God gone mad.

Modron Biology

Modrons Biology Dnd

The biology of a Modron is based entirely on their position in the overall hierarchy. They will not only gain more complex geometry in the form of increasingly more angles and sides to their shape.

Curiously their insides will become gradually more biological. All Modrons are a mix of biological and mechanical materials. It’s their place in the hierarchy of Modrons that designates the ratio. 

This makes absolutely no sense without context. So let us look at two sides of the Modrom Hierarchy spectrum. Remember that the Modrons all come in varying shapes and sizes, and these examples are solely based on their official art.

All sources say that their appearance is abnormal, unsettling, and weird. Alien in concept, no matter how humanoid it becomes. The only constant is the number of sides, dictating their rank.

A Monodrone is spherical with four limbs, a single eye, those obnoxious lips, and sometimes wings. They are the simplest of Modrons, and their body exemplifies this with their bodies made to be functional but not exaggerated.

They even come with a 48-word limit. I, personally, would explode with such a limited speech. There is an estimated population of 300 million Monodrones in the Modron society.

On the opposite spectrum, the Secundus is the highest ranked Modrons, second only to the creator of their race, Primus. As opposed to the simple spherical Monodrone, a Secundus looks like a very tall humanoid. Their long faces were only matched by their abnormally spindly fingers. There are only four Secundus in Modron society. 

The Modrons do not require breath, they have no need to consume food, and they don’t even get thirsty. Instead, the entire species eat a form of psychomorphic energy. It’s said to have the consistency of a thick jelly while emitting a faint inner light.

Modrons are hearty, with an immunity to mind-affecting effects, psionic-based attacks, and resistance to acid, cold, and fire. They also hold immunity to any magic that draws from the Positive and Negative Energy planes.

This energy is presumably harvested on their home plane of Mechanus. It is then stored in a large pool in Regulus, the divine realm of Primus and the largest city in Mecanus.

If a Modron dies, they immediately disintegrate. Then, somewhere, a Modron one rung lower on the ladder gets promoted in their place. When the domino effect reaches a Monodrone being promoted into a Duodrone, another Monodrone gets created in the Modron Cathedral on the center gear of Regulus.


The most potent and complex Modrons were considered of the Hierarch Cast. While there are almost double the number of castes in the Hierarch compared to the basic spread, not even all of them combined compare to the population of a single base caste.

For example, the lowest ranked Hierarch Modron, a Decaton, has a population of 100. Comparatively, the highest ranking base Modron, Pentadrone, has a population of 500,000.

Hierarchs all have the innate ability to duplicate a set list of spells. They share the following spells: clairaudience, clairvoyance, command, dimension door, teleport without error, and wall of force. They can perform these spells at will. 

furthering the gap between Hierarchs and base Modrons, individual ranks of Hierarchs were able to access more spells from different schools of magic. In honor of their glorious creator, any Modrons capable of Divine spells use the domains of Law, Protection, and War. Sometimes, Protection is replaced with Peace*.

Rank Spell List
Decaton Healing Spells
Nonaton Psionic Spells
Quintons, Octons Divine. (Peace*)
Quarton Arcane & Divine. (Protection*)
Septons, Hextons, Tertian Wizard & Sorcerer
Secundus All of the above

Incremental Danger, Modron Psychology

Incremental Danger, Modron Psychology

The higher a Modron’s rank and the more sides their geometry has, the more complex they become. A Monodrone can only do one simple task at a time. A typical example being they can relay a single message of up to 48 words.

This also translates to their attacks. While a Monodrone can only make one attack or action a round, a Duo-Drone can perform two attacks a round. A Pentadrone can make five attacks a round. 

Thankfully, excluding the Hierarchs, Modrons don’t hit particularly hard. Their weapons and fists are generally only capable of d4 damage. The danger is that the Modrons are usually skittering about their groups.

That does not mean there aren’t horrific tactics hidden among the notoriously neutral Modrons. For example, Pentadrones can surprise their enemies with nerve gas.

The highest ranked base Modron, the Pentadrone, is also the first of the hierarchy capable of the critical skill of improvisation. However, while they can act in ways beyond what they are ordered to do, they can not override Primus’ primary programming.

Occasionally, a defective Modron will use it to act outside of its initial programming or orders. These Modrons are relentlessly hunted and mercilessly destroyed on contact.

Due to this, they are separated from the Modron Hierarchy and lose their immunity to mind-affecting spells. They can be convinced to do things outside of Primus’ programming. This feat is made progressively harder the more complex the Modron is. 

Modron Society

Modron Society is separated into fourteen casts split into two categories. The five base castes are, in order of rank,: Monodrones, Duodrones, Tridrones, Quadrones, and Pentadrones. The Hierarch castes are composed of Decatons, Nonatons, Octons, Septons, Hextons, Quintons, Tertian, and Secundus.

The maximum number of each progressive rank dwindles progressively with over 300 million Monodrones and only four Secundus. The Base Ranks are all teaming with recruits, while no Hierarch grade exceeds 100 members.

Primus, godlike creator of the Modrons, rules above them all.

The Modron society functions much like other mechanics in that it is deceptively simple. Complexity is born from the simple structure they follow. They speak a highly precise language, incredibly complex and challenging to learn. It’s said to be based on ‘unique concepts’ down to having its own system of numbers. 

There is said to be Modron poetry out there. My wings to the bard who finds it.

Each Modron is compelled to obey the commands given by any Modron one rank higher. However, this does not mean they will ignore a Modron two ranks higher and above. Instead, they will see them as a potent version of the type of the species of Modron they fall back to.

For example, a Pentadrone will only take orders from a Decaton. However, say a Nonaton comes ’round to ask something of the Pentadrone. The Pentadrone will simply perceive the Nonaton as an exceptionally powerful Decaton. 

There is a caveat, however. A simpler Monodrone would be unable to comprehend the orders of a more advanced Decaton. 

All Modrons are aware of their creator, Primus. They hold a deep devotion to their godlike creator and follow his commands in the name of Order.

Should a Modron of a higher rank be slain, a member of the rank immediately below it will be promoted to the rank of the slain Modron. This will set off a domino effect until a Monodrone becomes promoted. At this point, a new Monodrone will be created to take its place in the newfound gap.

This includes Primus himself.

Modron Armies

Modron Armies

Modrons have 36 known armies. Each of the 16 regions of Mechanus gets its own. Another one for each of the four Secundus. There are three armies the nine Teritan share as secret police cause Modrons, of COURSE, need secret police. Finally, of course, Primus’s own nine armies, one of which was the royal guard protecting Primus’ tower.

These armies were not tiny affairs. In a single army, a Hexton controls 4 corps. Each of these four Corps is handled by 40 Pentadrones. The Hexaton will be in constant telepathic communication with all 160 of these Corps Commanding Pentadrone.  

Now hold on as we have a few more ranks to cover. Here are the brief notes. These Corps are further separated into two divisions, each with four brigades and its OWN four regiments. Each of the units is commanded by fewer and fewer Pentadrones until Quadrones and Officers start taking their place. 

This order and rank madness continues until you have a massive army of Monodrones outnumbering all commanders by a mile. Knowing Primus, probably a literal mile of Modrons.

Despite these vast numbers, Modrons are terrible at combat thanks to single-order Monodrones hardly doing much damage. However, a swarm of them can still turn the tide of battle to whomever they decide to side with. 

The issue is that, as beings of true Lawful Neutrality, they might not agree with the moral answer. Only the Lawful one, the one which brings Order and not necessarily peace. For example, in an ongoing ancient conflict known as the Blood War.

The Modrons are just as likely to side with the demons as the devils. They participate in these wars in an ultimately futile struggle to maintain the Order of the situation.

Great Modron March

Regulus, the divine realm of Primus, has been the departure site of every Great Modron March since the first cycle. Also known as the Modron Parade or the Mechanical ‘Meh’ Mystery Tour.

Like clockwork, all seventeen Outer Planes of the DnD multiverse get hit with Modron madness. Every 289 years, tens of thousands of Modrons swarm the realms. While the vast majority were Monodrones, as a Modron’s favorite cannon fodder, even Hierarchs joined the fray. 

Modrons in their March never seemed to actually investigate anything. Instead, they ignored anyone they came across, looking this way and that, supposedly circling the plane clockwise, then went on to their following location. 

Some claim they were reporting their findings of the plane’s reaction to them. Others pondered that it was a means to calibrate both the gears of the Modrons and the Order of the other planes. I believe it was to instill a sense of normalcy to them marching around every 300-odd years. 

After all, the one time a Rogue March happened, all the Planes were in disarray. That slightest shift in the routine became chaos, thus proving the need for Order. 

Some of these Marches take decades to complete, with the shortest recorded being merely months long. 

Modron March Itinerary

Modron March Itinerary


The March followed a predictable pattern through the 16 other Outer Planes in the Great Wheel of the Cosmos. 

First, the March would hit every gate-town in the Outlands one by one in its tour. They’d succeed in doing this in the most effective way possible by first entering one gate town. Then, they would use that town to enter its connected plane, probably testing the portal’s functionality. 

While there, they would March clockwise around the plane until they entered the natural portal to the adjacent plane. The Modron March would once more circle the plane, emerging from THAT plane’s gate-town where they would progress to the next Gate town in the outlands. 

This process is repeated until every one of the Outer Planes is hit by this peculiar display. Of course, maybe Primus is just showing his babies off.

It starts in the Mechanus gate-town of Automata heading to Arcadia, the gate-town to Mount Celestia. The March will proceed through every one of the planes and gate-town clockwise. One by one, the Outer Planes will be hit until they reach their final destination, Archeron, where they will take a portal to Mechanus. 

Every Great Modron March follows this same predictable yet efficient pattern.

Modron March Ranks

The higher ranks take to their jobs with fruitless abandon. Still, their numbers were notably slim as they have several significant unknown tasks scattered across Mechanus. Should the March be slaughtered and only one survives, it will return as a Quinton. 

A single Quinton usually leads this pack, with the March always promoting itself to replace the Quinton until the end. A single Hexton acts as the Modron March Minister of defense, and a Septon gets the grueling task of ‘handling it.’ 

Four Octons, each assisted by nonatons, commanded one quarter each of the March. Decatons were required to translate the complex commands of the Hierarchs we just mentioned down to the base Modrons, as the poor things can’t understand a word of the mechanical bureaucratic madness. 

For the Base Ranks of the March, at least fifty Pentadrone are kept actively patrolling the lower base Modrons. Quadrones act as the champions and elite warriors of this rag-tag March. Meanwhile, the Tri-Dones and duo-Drones act as the generals for the thousands upon thousands of Monodrones that make up the vast number of the Order battalion. 

Very few Monodrones have the honor of returning to Mechanus after a March. May Primus have Order on their soul.  


dnd modrons primus

Frustratingly little is known about Primus. He is constantly tinkering in the Tower of Primus in Mechanus. Situated on the divine gears of Regulus. He is the godlike power of his own realm. Not even Orcus could kill him permanently. 

While the rare deity capable of being killed, a Secundus will immediately evolve into a new Primus. As a plane of Order, redundancy reduction, and accordance with specific numerical systems. Many of these systems are of his own erratic invention.

It can be assumed Primus lives on in this constant Modron cycle. Some claim he is a mere mortal who invented their way to greatness.

The entire purpose of the Modrons could be to act as the perpetual life for the Mad God Primus and the minions to his crazed delusions. 

Some legends say Primus is now no more than a mad god imprisoned for all eternity inside a Plane of his own blood, flesh, and tears. Forever keeping himself alive through the possession of Modrons should he be killed. So mad, he believes himself the god of all that is now, has been and forever will be. Ao probably wasn’t happy with that stunt.


Every spot on the alignment scale has its own realm in the Outer Plane to represent it. In this array of alignment areas, the Clockwork Nirvana of Mechanus represented Lawful Neutral. As its full name implies, it is an infinite plane of interlocking gears.

As an apt representation of Lawful Neutral Order, the plane was an infinite number of interlocking gears, each at least 1000 miles/1,609 kilometers in diameter. In perfect Order, the gears turn in slow synchronic serenity.

They are crafted by one of the finest creators, and as such, every angle in the interlocking sections of these gears is made of perfect right angles.

Each disc had its own gravity spear, allowing for the habitation of the gear’s top and bottom. Provided it wasn’t crammed up against another continent-sized gear in the endless mechanism only Primus understands. 

The void was filled with an artificially introduced atmosphere outside these spheres, allowing wanderers easy flight and breathing. In fact, as a plane of law and Order, a balanced pattern could be seen even in its resources.

Equal amounts of every aspect and element. The darkness and light are kept balanced like a metaphorical yin and yang. As are the four elements collected in eternal union.

Nothing in Mechanus is introduced without its opposite being kept in equal measure. 

A perfect society is not without its drawbacks. The existence of pleasure requires, in equal balance, pain. Lucky for you, there is no pain, at least!

However, the closest form of passion to be found by its inhabitants, the Modrons, were finding their place in Primus’ infinite design. Visitors to the realm might bring their whimsy. Still, they will not be well received by its inhabitants, minus the wayward rogue Modron. 

Mechanus is full of ‘lesser’ or ‘subservient’ Modrons. While not fully classified as a Modron, they could only have been made by Primus or the highest ranked Hierarchs, making them count in my book. 

These include the Coggles, an adorable sounding but massive sapient gear that will move around Mechanus. They delight in popping themself in and out of clockwork, almost like some Gear elemental. 

Gear spirits work to maintain the many cogs and gears of the realm. They even kept them spotless. Finally, Moignos are strange two-dimensional creatures that supply calculations on the gear movements of the plane.

They aren’t harmless, though. Hilariously, the Moignos nearly conquered Mechanus. Thankfully, however, the Modrons convinced them to calculate Pi, which the Moignos resistance still focuses its efforts on calculating. 

I much rather a place run by goofy-lipped mechs rather than pure math. Unfortunately, rumors state a Pure Math dimension is said to lurk somewhere in the space between the Positive and Negative Energy Planes. The legends of this horrid place continue to haunt my nightmares.

Modron Time

Modron Time

Modrons follow a time cycle known as a Grand Cycle. This cycle is based on how long it takes for the largest gear in the plane to turn once. This great and glorious gear takes seventeen years to make one turn. After seventeen of these turns, or every 289 years, a glorious Great Mordun March occurs. 


The most significant realm in all of Mechanus, this place is a big deal even to the generally apathetic Modrons. It is the Divine Realm of Primus and the birthplace of the Monodrones from which all Modrons grow.

Being Primus’s home, it is understandably the most prominent spot in the Mechanus with a recorded 64 cogs. As the One and the Prime is a massive nerd, this lends the theory that Mechanus works on a 64-bit system.

The cogs were engineered in a pyramid shape that rotated around a massive axis at its center. This axis is reportedly as large as the Spire in Outlands. In the divine realm in the land of law and Order, each gear had numerous buildings dedicated to enforcement, record-keeping offices, and courthouses.

Primus, again clearly having studied Database Design, has reduced redundancy by making each building serve the same function being identical. 

The Modron Cathedral is located on the central gear. It holds not only the site where new Modrons are created but the most exemplary working model of the multiverse on this side of Ao.

In addition, a large pool of psychomorphic jelly, the one source of food the Modrons reportedly eat, is located here. All harvested Modron Jelly, outside of marching rations, gets stored here.  

The Modrons constructed Regulus in precisely 289 years down to the perfect millisecond. I believe that it is due to this reason, and Regulus being the starting point of every Great Modron March, that the first Great March happened the moment Regulus was completed, forever scheduling it for every seventeen turns of the great wheel. 


Question: Why Do Modrons Have Such Puffy Lips?

Answer: There are many theories as to why the art style has decided to make the lips the most humanoid feature of the lower-ranked Modrons, but the most credible theory is a misguided attempt to make the humanoids of the other planes less put off by their inhuman appearance. 

Question: What is the Purpose of the Great Modron March?

Answer: While the purpose of your regularly scheduled March is unknown, an ancient tome known as a ‘second edition D&D adventure’ by the same name as the March.

It was set in the Planescape series of AD&D modules to be precise. In this adventure, the demon lord of the Undead Orcus wanted to become a deity. As you do. He killed Primus and temporarily stole his clockwork throne. 

An unpredicted march nearly 200 years ahead of schedule was enacted to search for the Wand of Orcus. This was Orcus’ main weapon and, befitting his stature, considered a Major Artifact. It’s so powerful that even touching it has a chance to kill you. 

Question: What’s the Weirdest Modron Lore You Found?

Answer: There is a theory surrounding the original creation of the Modrons. This theory posits that there was a species of insectoid creatures with a complex hive mind. It is believed they learned to store their energy in a pool in Regulus.

They can then recover it to sustain their immortality. Over time, this process birthed Primus as the absolute whole of the hivemind. These insects were thought to be the initial biological components Modrons are noted as having.


Modrons and their plane of Mechanus have proved utterly fascinating to me. Where Devils are the exact opposite of Angels as beings of Law, Modrons could potentially consider the exact opposite of a Fey as beings of Neutrality. Fey often being Chaotic Neutral, however, the Wylds is a Mirror Dimension. Not an Outer Plane. 

Still, this helps me to understand to whimsical nature of Mechanus. It might be a land of pure Order and Law, but my geeky love of anything technological made me absolutely delighted to see a land of Clockwork full of uniquely designed species all bubbling with computer logic and database design. 

As of right now, 5e adventures including the Modrons are pretty slim if not nonexistent. The only one I could find dates back to the Second Edition of D&D. Something I personally consider a shame, as I think the gears are ticking towards another Great Modron March. 

If we are lucky, maybe we’ll get some answers to what the regularly scheduled Marches are all about. That adventure only proved Primus will send one out on a whim if spite and death are on the line.

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