Aetherius

Aetherius is the realm from which Aedra such as the Nine Divines originate. It can be construed as the inverse of Oblivion, from which the Daedra rule; conversely, Aetherius is the realm from which the Aedra are connected. Oblivion is considered the dualistic inverse of Aetherius.

It is the plane of pure magicka, and it's the realm where magicka was said to originate. Common belief is that souls ascend to this location upon death. The Imperial Geographic Society has this to say about it:

"It is aetherial energy that infuses our daily existence, from highest to lowest, and gives all the races of men, mer, and beast common purpose. Its magic brings the rain to the fields, love to our hearths, and scientific principles to our technological industries. It gives us the very Sun itself. Finally, Aetherius is the home to the Aedra, those cornerstones of the Mundus whose aspects we see in the temple, in lordship, and the high walk of heroes."

Realms within Aetherius
Though it is known that Aetherius contains a large number of planes within itself, only two are specifically known.
 * Sovngarde
 * Mantellan Crux - a self-contained prison for the Mantella.

Reaching Aetherius
It is substantially more difficult to reach Aetherius than it is to reach the Void of Oblivion. The only two successful trips there occurred firstly during the Reman Dynasty, and secondly by the "Sun Birds" of Alinor. From the Reman Dynasty, the Royal Imperial "Mannanauts" were obtained, and from the Sun Birds, the Orrery of Firsthold. It is also rumored that the Dwemer may have reached Aetherius in the past, as well. Some believe that the stars, including Nirn's sun, Magnus, are direct portals to Aetherius that were created when Magnus and the Magna Ge fled back to Aetherius during the creation of Nirn. Also, the agent sent by Uriel Septim to Daggerfall to ensolve the murder of King Lysandus was transported to Aetherius by Nulfaga in Castle Shedungent in order of find the Mantella. The Dragonborn reached Sovngarde, a realm of Aetherius, to defeat Alduin in the main quest of.

The Hero of Daggerfall entered Aetherius' sub-realm Mantellan Crux to extract the Mantella for use against the Underking. The realm exists as a massive labyrinthine puzzle. Sheogorath is encountered here, in his parlor. Although, in later titles, Sheogorath became associated with the realm of Oblivion, Aetherius' converse, he was not included as such in Daggerfall.

In, Aetherius is mentioned in passing in the form of a Heaven Stone named Aetherius Stone. It is located northwest of Skingrad and slightly south of Bleak Flats Cave. Activating it Fortifies Magicka 50 pts and adds Resist Magic 20%.

The priestess at Helgen commends the souls of the Dragonborn and of the other prisoners to Aetherius, regardless of race.

When seeking entry for the first time to the College of Winterhold, the conversation with the watcher of the bridge may turn so that this response may be given: "I want to unravel the mysteries of Aetherius," to which she responds with acknowledgement that it is a noble goal to wish to understand the plane from which all magic comes.

Quests

 * Journey to Aetherius -
 * Sovngarde -

Behind the Scenes
It is likely that the name came from the Aetherius Society, a religious cult formed in the 1950s.