Mundus

Mundus, the Mortal Plane, is the plane or realm of existence that contains Nirn, it's moons, Masser and Secunda, as well as all other Aedric planets. Surrounding it is Oblivion, and surrounding Oblivion is Aetherius. Mundus was created with the help of divine beings known as Et'ada. The idea was brought up by Lorkhan and designed by Magnus. Those who helped in its creation are known as Aedra. Those that didn't help in the creation of Mundus are known as Daedra. Some of the Aedra committed their entire being during the construction process, forming the planets. These beings are known as the Divines. Before Mundus was finished, Magnus discovered that Lorkhan was draining his power to create Mundus, and fled to Aetherius, ripping a hole through Oblivion. This hole became the sun. Some of the other Et'ada followed Magnus, ripping more holes in Oblivion which became the stars. Some Et'ada had used so much power that they had to stay, and they later evolved into the Ehlnofey.