The majority of the modron people consists of the monodrone, the lowest caste. These beings are responsible for the lowest tasks, serving as general laborers, messengers for the modrons through the planes, and soldiers in the 36 modron armies.
As all modrons, monodrones resemble odd crosses between constructs and living beings, apparently having fleshy internals covered almost completely with metal plates. Monodrones are the smallest caste of modron as well as the lowest, being only 2 feet tall and weighing barely 40 pounds. They have the form of perfect spheres, with a single eye and mouth at the front of their bodies, two spindly legs falling from their undersides, and two equally-spindly arms emerging from the top of their form. Some monodrones possess a pair of wings instead of these latter limbs, allowing them to fly; such monodrones can use their legs for manipulation when necessary.
Monodrones can be found all throughout Regulus, outnumbering the entire rest of their species by nearly three to one. Literally single-minded, they perform the tasks given to them by their duodrone superiors ceaselessly, not stopping until ordered even when continuing is futile or unnecessary. Monodrones can only follow a single command at a time, however, abandoning an old task once ordered onto a new one. Thankfully, they have no need for sleep and draw sustenance directly out of the air at all times, as otherwise they would have to be ordered to perform both when necessary. This caste is only barely intelligent, being entirely incapable of independent thought to any degree. As all modrons, monodrones acknowledge only their direct superiors as modrons, seeing duodrones as perfect examples of order and barely aware of the existence of other castes of modron, even when directly observing them.
- Dragon #354 - Return of the Modrons, pp.34-49
- Planescape Campaign Setting - Monstrous Supplement, pgs.16,18-19