Modron (Dungeons & Dragons)

In the fictional multiverse of the Dungeons & Dragons fantasy role-playing game, Modrons are creatures native to the outer plane of Mechanus. Modrons resemble geometric shapes with humanoid limbs and represent a living, physical manifestation of Law without regard to Good or Evil. They follow a strict hierarchy, with each rank reporting to the rank directly above it, and issuing commands to the ones ranking beneath it. For example, a quadrone modron will report to a pentadrone, and command several tridrones.

Advanced Dungeons & Dragons 1st edition (1977–1988)
Modrons were created by Francois Marcela-Froideval, working from suggestions by Gary Gygax. They first appeared in 1983, in the AD&D 1st edition Monster Manual II, which introduced the base modrons (including the monodrone, the duodrone, the tridrone, the quadrone, and the pentadrone), the hierarch modrons (including the decaton, the nonaton, the octon, the septon, the hexton, the quinton, the quarton, the tertian, and the secundus), and Primus (The One and the Prime).

Advanced Dungeons & Dragons 2nd edition (1989–1999)
In the 2nd edition of Advanced Dungeons & Dragons, the Plane of Law was renamed Mechanus (instead of Nirvana) and the depiction of Modrons introduced clockwork features (expanding on the description of Nirvana as a plane of cogwheels in the 1st edition Manual of the Planes). The monodrone, the duodrone, the tridrone, the quadrone, the pentadrone, the decaton, the nonaton, the octon, the septon, the hexton, the quinton, the quarton, the tertian, the secundus, and Primus appeared in the Planescape Campaign Setting boxed set (1994). In his review of the Planescape Campaign Setting boxed set, Gene Alloway mentioned the modrons as an example of "the old, tired and previously foolish" which the set "breathes new life and meaning into". Scott Haring, in his review of set for Pyramid, also mentioned the modrons as "once-silly" and "rescued from an old 1st Edition AD&D hardback and given a new background and purpose that makes a lot more sense".

Planescape also introduced rogue modrons: modrons who have left Mechanus and broken their connections to the other modrons. Modrons were made a playable character race in The Planewalker's Handbook (1996), and a rogue modron named Nordom (voiced by Dan Castellaneta) could join the player's party in the computer game Planescape: Torment.

Dungeons & Dragons 3.0 and 3.5 edition (2000–2007)
In the 3rd edition of Dungeons & Dragons, modrons largely faded from prominence, their place as the primary representatives of lawful neutrality taken by the antlike, expansionist formians and the robot-like, implacable Inevitables. They have received only a passing reference in the Manual of the Planes sourcebook, with a more detailed explanation in the web enhancement. In Dragon #354, an article was published on the recent history of the modrons, as well as detailed game statistics for the base modrons (the monodrone, the duodrone, the tridrone, the quadrone, and the pentadrone, as well as the messenger monodrone and the winged quadrone) and PC modrons such as the exiled modron.

Dungeons & Dragons 4th edition (2008–2014)
The 4th edition brought many changes to the cosmology of Dungeons & Dragons. In the article Creature Incarnations: Modrons in Dungeon #186, the Modrons are described as "cells" of the unknown being Primus and are classed as Immortal Animates. The monodrone brickguard, the duodrone marcher, the quadrone enforcer and the modron hierarch are described.

Dungeons & Dragons 5th edition (2014–)
Modrons are prominently reinstated into the lore in the 5th Edition Monster Manual, which includes stats for the monodrone, the duodrone, the tridrone, the quadrone, and the pentadrone, and a brief write-up describing them in terms similar to those in 2nd Edition.

Hierarchy
The hierarchy of Modrons, ranked from lowest to highest, is as follows:

There are only limited numbers of hierarch Modrons in existence, there being only one Primus, four (two squared) Secundi, nine (three squared) Tertians, and so on. In order to keep this number stable, upon the demise of a Hierarch, one of a lower rank is promoted upwards, and the resulting void filled by another promotion, and so on. When the promotion reaches the Monodrone level, a new Monodrone is spawned from the Energy Pool in the center of Regulus to fill the void left by the promotion of a Monodrone into a Duodrone. This means that at any given time, there are 385 hierarch Modrons in existence, including the Primus.