Nemausus

Nemausus, sometimes called Menausus, was the former third layer of Arcadia before it was absorbed into Mechanus.

Geography
Nemausus had rich forests and verdant fields, all perfectly organized and aligned. No cities existed in the realm, but modron fortresses and abandoned training camps could be found scattered in the otherwise pristine landscape.

The realm could still be reached by gates from Buxenus, but access through those gates was extremely restricted by the Harmonium. Officially, the faction did not want to worsen the situation of the former layer's separation from Arcadia. Moreover, Nemausus was the site of the faction's most bitter defeat, which was sufficient reason for the Harmonium to want to keep it as secret as possible.

History
Before its separation, Nemausus was the most beautiful of the three layers of Arcadia.

Nemausus had been separated from Arcadia for millennia. The reason for the separation was often attributed to a large expansion of its formian inhabitants and their ruthless adherence to law. However, other sages maintained that the real reason for its separation were the training camps kept by the Harmonium. Designed to forcefully convert creatures of chaotic tendencies to their harmonious view of the universe, the Harmonium camps fouled the good nature of the layer and pushed it into neutrality.

When the layer separated, the imprisoned chaotic creatures broke free, also mingling their natures into the plane. For that reason, Nemausus retained a level of disorganization and recklessness unlike the rest of Mechanus.

The realm was constantly invaded by troops controlled by the Harmonium in attempts to reclaim it for Arcadia. However, those attempts were often contaminated with selfishness and evil, which meant that there was very little chance that it would ever come back to Arcadia. The layer had become so ingrained in Mechanus that it was often difficult to distinguish it from the rest of the plane.

Inhabitants
There were still petitioners from Arcadia in Nemausus. Driven by the chaos inserted into the realm and the hatred for its controlling factions, they dwelt underground in warrens that were deep enough to reach the very cogs of the plane.