I was a huge math nerd as a kid. I think I must have been just 5 or 6 years old when I first got my hands on Flatland, and I drank it up like a parched man in a hot desert (having no idea until many years later that it was an allegory for classism and sexism in Victorian England), and the discovery of a quasi-sequel called Sphereland (sadly, not in print right now) delighted me even further.
So maybe you’d expect me to be more into modrons than I am. But when a reader recently told me he planned to run a campaign in Mechanus, the plane of pure law, and thought he wasn’t doing the modrons justice, I had to confess: I hate them. I have a great appreciation for silliness, but modrons have always struck me as just too silly, like whoever came up with the idea of Mechanus envisioned it as something out of The Phantom Tollbooth or Donald in Mathmagic Land.
Modrons are constructs, automata with vaguely mathematically inspired bodies and weirdly humanoid faces (with, in the illustrations of the fifth-edition Monster Manual, disturbingly full lips). The more advanced the modron, the more it can multitask, and the more authority it has over other modrons. All modrons possess natural armor, above-average Dexterity, 120 feet of truesight, and the features Axiomatic Mind and Disintegration.
One of the many peculiarities of modrons is that they’re denizens of an outer plane, yet their challenge ratings top out at 2. How many low-level adventurers are going to travel to Mechanus? I wonder whether these creatures must exist at least primarily for the sake of background decoration. They’re not going to pose a challenge to the player characters who encounter them except in great numbers—legions.
The monodrone is the simplest, lowest-level modron. It can fly, but it doesn’t have any way to avoid opportunity attacks, so the tactic of holding station in the air, flying down to attack and flying back up is suboptimal. Instead, it uses its flying movement to make ranged javelin attacks over opponents’ cover, traverse vertical distance and ignore difficult terrain. (Not that there’s any difficult terrain in Mechanus.)
Although it has average Wisdom, its Intelligence is animal-level: it chooses targets indiscriminately and has no ability to adapt to changing circumstances. Whatever its orders are, it follows them to the letter.
It carries a dagger and a javelin, but note that the attack and damage of the javelin attack are based on its Dexterity. Javelins are not finesse weapons, so a monodrone using a javelin as a melee weapon should actually have +2 to hit, not +3, and do 1d6 piercing damage, not 1d6 + 1. Also, logic dictates that a weapon you throw is a weapon you no longer have. So we have a simple formula for monodrone combat: approach to 30 feet, throw the javelin, then close to melee range and fight with the dagger from that point on. If at any time a monodrone manages to defeat or displace its opponent, retrieve javelin, GOTO 10.
Monodrones have no independent judgment, and since modrons exist in infinite supply, they have no self-preservation instinct. A damaged monodrone follows its instructions until it’s destroyed.
Duodrones are only marginally more intelligent than monodrones, and they can’t fly. They can attack twice in one action, but they must do so with the same weapon: either two javelin attacks or two pummeling attacks, not one javelin and one pummeling. Also, just as with the monodrone, the duodrone’s Dex is slightly higher than its Strength—but unlike the monodrone, the duodrone carries no finesse weapon for melee combat.
For this to make any sense at all, I think a duodrone has to carry several javelins into battle, and the number must be odd (not even, and you’ll see why in a moment). Historically, in Classical times, soldiers carried three to five javelins onto a battlefield in their off hands or—rarely, and only toward the end of the period—in a quiver. So let’s give the duodrone five javelins, because in the illustration, its fingers are long and skinny; it can probably hold a big bundle.
When combat begins, a duodrone approaches to 30 feet and throws two of its javelins. If its opponent closes with it, it uses one of its remaining javelins as a melee weapon (remember to change the attack modifier to +2 and damage to 1d6); if not, it hurls two more, and at that point it still has one remaining that it can use for melee fighting. A duodrone can fight with its fists, but that doesn’t mean it should. A javelin does a bit more damage, so it will prefer to have one left over.
Like the monodrone, a duodrone will retrieve its thrown javelins whenever there’s a break in the action—but only if it can pick up two that have landed in the same person, place or thing. Picking up just one javelin would mess up the duodrone’s system. Also like monodrones, duodrones don’t retreat, no matter how much damage they take.
Nothing distinguishes a tridrone from a duodrone except its Multiattack (three attacks, meaning it always wants to carry 3n + 1 javelins—we’ll start it off with seven, since it has two extra hands to carry them in) and its near-average Intelligence, which allows it to adapt to a changing situation. Tridrones still won’t retreat to save themselves, but they will position and reposition themselves on a battlefield to take advantage of terrain, cover, chokepoints and other features with potential tactical benefits, and they’ll order lesser modrons to do the same. They’ll also respond appropriately to obstacles and hazards created by their opponents. However, they lack the Intelligence to create tactically beneficial features, obstacles or hazards themselves; they can only take advantage of ones that already exist.
Monodrones and duodrones aren’t intelligent enough to Disengage independently, but with a tridrone on the field to give the order, they can hear it and obey. Tridrones will cover the retreat of monodrones and duodrones that have Disengaged to take a new position. Also, it takes at least a tridrone to recognize an attack that does extra damage to constructs, such as a mace of smiting. Once an enemy makes such an attack, a tridrone will focus all its attacks on that enemy and order the other modrons under its command to do the same.
Quadrones are archers whose Dexterity and Multiattack both strongly favor ranged attacking over melee, so unlike tridrones, quadrones will lead from the rear, not from the front line. If someone needs to run interference, quadrones will order tridrones to do that. To the fullest extent possible, quadrones will maintain position between 35 and 80 feet from the nearest opponent, someplace with a good view of the whole battlefield and as much cover as they can get. From there, they’ll rain arrows down upon their foes, at a rate of four shots per turn. Twenty is a good number of arrows to give them.
When a quadrone runs out of arrows, five combat rounds have gone by, and that’s enough time for a quadrone to realize that things are not going as they should. At that point, they’ll order a tactical retreat toward a location with more modrons, including more quadrones, with any surviving tridrones in their unit acting as rearguard.
Pentadrones, despite being at the top of the modron hierarchy (as far as the Monster Manual goes, at least—we can hypothesize the existence of infinite types of modron), are brute fighters. If you’re using a battle grid, remember that pentadrones are Large creatures, so they take up more space.
Pentadrones march right up toward the front line of combat, let loose a cone of Paralysis Gas as soon as they can catch at least three enemies in it (not having the Intelligence to direct it specifically at enemies who look more susceptible to it), then start whaling away with their five arms, targeting those who have not succumbed to paralysis. They leave paralyzed targets to the lesser modrons under their command, which need advantage more than the pentradrones do and which are less equipped to battle those tough enough to make their Constitution saves. They continue attacking with their arms until their Paralysis Gas recharges, at which point they use that weapon again.
Pentadrones, like tridrones, will cover the retreat of lesser modrons if such a thing becomes necessary, but even they don’t retreat simply because they’ve taken serious damage. They order a retreat only if combat lasts more than five rounds, at which point the quadrones under their command will have run out of arrows.
When pentadrones lead a battle with other modrons under their command, monodrones, duodrones and tridrones will forgo their ranged attacks in order to seize the opportunity of attacking a paralyzed opponent at melee range for the “every hit a crit” benefit. When there’s no paralyzed opponent within their movement distance, they go back to their normal javelin-hurling routine, if they have any javelins left.
Finally, let’s talk about why lawful neutral beings are engaging in combat at all. This is a topic I’ve discussed before, when analyzing myconids. Lawful evil beings will want to kill trespassers by default, but lawful neutral beings are interested in maintaining order by the simplest, most straightforward methods available, and fighting is rarely simple or straightforward. Their default disposition toward strangers is indifference, not hostility. They’ll leave your PCs alone unless and until the PCs break the modrons’ rules or start causing a ruckus.
Unfortunately for the PCs, modrons aren’t equipped with features that would make them good at grappling. They can choose to attack to subdue rather than kill (see “Knocking a Creature Out,” Player’s Handbook, page 198), and I think this would be consistent with the values of the plane of pure law. Why kill what you can capture and put on trial? Trials are probably the pinnacle of public entertainment in Mechanus.
But also note the fine print on that page: only melee attacks can be nonlethal. Duodrones and, especially, quadrones are optimized for ranged combat. Small problems can be dealt with by monodrones that can swarm troublemakers and bring them back as captives. But a problem too large for monodrones will often involve modrons that aren’t going to compromise their combat effectiveness to avoid killing their enemies. And the modron method of solving problems is simple: throw more modrons at it. Mechanus never runs out.
Next: displacer beasts.