Nirn

Nirn is largely known by otherworldly beings as Mundus, or the mortal plane. The exact reasons and specifics of Nirn's creation are largely debated; however, all agree that the deity Lorkhan was the mastermind behind its creation. There are many theories on how he created Nirn; ranging from the other Aedra agreeing to willfully help, to Lorkhan tricking them into it. However, it is universally acknowledged that the Aedra gave their energy and power for it, and that the majority gave up on the project after realizing the cost, and that those who didn't became the Eight Divines, or the Earth Bones. In the Elder Scrolls IV: Oblivion it is revealed by Mankar Camoran that Nirn is possibly an expansion of the realm Oblivion, although this is likely just the ramblings of the Mythic Dawn.

Nirn is orbited by twin moons, Secunda and Masser.

It should be noted that as Masser (Nirn's larger moon), revolves around Nirn. It can be spotted that in Oblivion Secunda (Nirn's smaller moon), does actually revolve around Masser. Thus some opinions say that Masser is actually a planet. But since it is revolving around a planet it is a bio-revolving moon system.

Geography
The notably large continent on the planet is called Tamriel, which is where all of the Elder Scrolls games take place. With an another similarly large continent to the east of Tamriel, this continent is named Akavir. To the North of Tamriel is the cold barren land called Atmora, which is where the Nords of Tamriel hailed from. To the west of Tamriel lies Yokuda, which was the former homeland of the Redguards of Tamriel.

Tamriel
Tamriel is geologically interesting as it has mountains, tundras, cold deserts, hot deserts, swampy regions, grassland, tropical rainforests and an arguably large volcano. The diversity of biomes is unique as the hot desert is bordered by cold mountains to the north.

Tamriel also holds home to a series of islands called the Summerset Isles and is where the Altmer, or High Elves hail from.

Yokuda
Not much is known about Yokuda since it was nearly obliterated in a cataclysmic event, but it seems to have a dull, rocky, hilly landscape.

Atmora
Atmora is a barren and freezing wasteland. It is this extreme cold that caused the water of the Sea of Ghosts that borders Tamriel and Atmora to become icy.

Akavir
Next to nothing is known about the geography of Akavir.

Nirn Нирн