Mechanus is where perfectly regimented order reigns supreme. It consists of equal measures of light and dark, and equal proportions of heat and cold. On Mechanus, law is reflected in a realm of gigantic clockwork gears, interlocked and turning according to their measure. The cogs seem to be engaged in a calculation so vast that no deity can fathom its purpose. Some theories hold that they are the clockwork of time throughout the cosmos—that time itself would stop if the gears ceased their turning. Other theories propose that the cogs uphold the basic rules and order of the cosmos.
Modrons are the primary inhabitants of Mechanus and maintain its intricate clockworks. The plane is also home to the creator of the modrons: a godlike being called Primus, whose realm is called Regulus.
Mechanus has no distinct layers. Each turning cog has its own force of gravity pulling toward its center, with structures built on the faces of the cogs. Some of the cogs are like small islands, while others are hundreds of miles across.
Mechanus embodies absolute order, and it influences those who spend time here. Individual consciousness is subordinated to the search for perfect order, and “I” is ultimately subsumed into “we.”
An adventure on Mechanus might lead characters to examine their individual egos in the light of the adventuring party. It might challenge a character to set aside personal goals for the benefit of the group (or the greater cause of cosmic law), or alternatively it might encourage characters to assert their own individual identities, distinct from the party and possessing their own goals and needs.