Mechanus

On Mechanus, law is reflected in a realm of clockwork gears, all 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. Mechanus embodies absolute order, and its influence can be felt on those who spend time here. Modrons are the primary inhabitants of Mechanus. The plane is also home to the creator of the modrons: a godlike being called Primus. 
Imposing Order- At the end of each long rest taken on this plane, a visitor that isn’t lawful neutral must make a DC 10 Wisdom saving throw. On a failed save, the creature’s alignment changes to lawful neutral. The creature’s alignment reverts to normal after one day spent on a plane other than Mechanus. Casting the dispel evil and good spell on the creature also restores its original alignment. (Source: DMG D&D)
Mechanus was connected to the Prime Material Planes via the Astral Plane, and to the Outer Planes of Arcadia, Acheron, and Sigil by portals which appeared once every revolution of the gears they belonged to. The period of rotation depended on the size of the gear, but a typical period was twenty days. The portals stayed open for exactly one day. There was one portal to Sigil, located at the centre of the featureless bottom side of a large gear, that was continually open. One of the gears is the home of Emos and there helper Lifeline, where they watch over the souls of there followers.
Inhabitants- The only creatures native to Nirvana were the modrons, a race of beings organized in a rigid caste system and ruled by Primus, the One and the Prime. The most common modrons were the monodrones, single-function drones used as common laborers, servants, or soldiers. (https://forgottenrealms.fandom.com/wiki/Mechanus)

Alternative Name(s)

The Clockwork Nirvana

Type

Dimensional plane

Location under

Outer Planes

Owner/Ruler

Emos

Ruling/Owning Rank

Deity