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.

Ecology
There were fourteen types of modrons: monodrones, duodrones, tridrones, quadrones, pentadrones, decatons, nonatons, octons, septons, hextons, quintons, quartons, tertians, and secundi. Each type had a corresponding shape; the higher ranking the modron, the more complex. For example, monodrone bodies were spherical, whilst quadrones were cubical. The modrons served Primus, godlike ruler of Mechanus. 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.

Culture
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 existance of Primus, however. Modrons were unwavering in their devotion to order, departing Mechanus to complete strange tasks in the name of law.