Modron

Modrons were a race of immortals known for their zealous adherence to the principles of law and order above all else. Just as fiends were considered the embodiment of evil and celestials the embodiment of good, so were modrons the embodiment of the universal principle of order.

Description
A modron's appearance was varied and depended on their position in modron society. The most common appearance of a modron was as a geometric shape, such as a sphere or cube. The amount of sides as well as structure determined a modron's position in their society. The more sides a modron had, or the more complex their structure was, the higher they were ranked. The highest ranked modrons were humanoid in appearance.

Combat
Modron armies battled the forces of chaos and entropy across the multiverse. Modrons used logic in developing their tactics and follow proven battle strategies. Modrons were relentless in battle, fighting without compassion or remorse, and were willing to sacrifice themselves to achieve their objective.

Abilities
All modrons were immune to mind-affecting, emotion-affecting, and magic that drew upon the Positive Energy or the Negative Energy plane. They were resistant to cold, fire, and acid. Hierarch modrons had the innate ability to duplicate the effects of clairaudience, clairvoyance, command, dimension door, teleport without error, and wall of force spells at will.

Society
Modron culture was simple. Each modron obeyed all commands given to it by any modron one rank higher. These commands were obeyed without question. Modrons were only aware of modrons one rank higher than they were, for example, a quadrone could issue orders to tridrones, duodrones, and monodrones, but would only obey orders from pentadrones. If a modron higher in rank than a pentadrone issued an order to a quadrone, it would view it as some exceptionally powerful pentadrone. All modrons were aware of the existence of Primus, however. Modrons were unwavering in their devotion to order, departing Mechanus to complete strange tasks in the name of law. The modrons served Primus, godlike ruler of Mechanus.

There were fourteen castes of modrons, divided in two major categories:

Relationships
The lillendi, guardians of the Infinite Staircase, held a grudge against the modrons for reasons unknown. Slaadi detest modrons and have waged epic battles against the forces of Mechanus for millennia.

Physiology
Despite appearing as mechanical constructs, modrons were not entirely mechanical. Every modron had a mix of biological and mechanical parts, the degree of which was determined by their place in modron society. Lower ranked modrons had more mechanical components integrated within them than higher ranking modrons.

Most modrons had no sense of smell, and no modron had a sense of taste. Modrons used auditory and tactile sensors. Since modrons communicated telepathically while in Mechanus, their sense of hearing was primarily used to detect sounds and to facilitate communication with non-telepathic visitors to Mechanus. Modrons felt pain and physical contact via their tactile sensors and were able to inhibit this as required. All modrons had eyes, with hierarchs having two or more eyes, allowing them to have a full field of vision.

Unlike most other creatures, modrons had no need to breathe or consume food and liquid to survive. Modrons required regular intake of a unique form of psychomorphic energy. It had the consistency of thick jelly and emitted a faint inner light. It was harvested by monodrones and stored in a large pool in Regulus. Modrons had to intake this substance every few weeks or else begin to degrade.

History
The giant deity Annam All-Father acquired the secret of rune magic for his people from a high-ranking modron by winning a game of lots about a thousand years after the giants' Thousand Year War against the dragons. Mechanus and the modrons were discovered by Netherese explorer and archmage Lady Polaris around, who also magically bound and employed them as guards.

Around that same time, a group of properly operating (albeit degraded) modrons had been left stranded in the Labyrinth in the Underdark after being separated from the previous Great Modron March.

Modrons were sometimes summoned by Calishite mages, and could be encountered in the city of Waterdeep.