Hermaeus Mora

Hermaeus Mora is the Daedric Prince of knowledge and memory, his sphere is the scrying of the tides of Fate, of the past and future as read in the stars and heavens. He is not known for being evil or good, but he seems to be the keeper of both helpful and destructive knowledge. Also called the Demon of Knowledge, he is vaguely related to the cult origins of the Morag Tong if only by association with his sibling, Mephala. He seems to only ever appear to Mortals as a void of darkness, or a mass of dark bubbles with octopus eyes and tentacles.

Plane of Oblivion
As recorded in "The Doors of Oblivion", Hermaeus Mora maintains a realm called Apocrypha, where all forbidden knowledge can be found. It is an endless library, with shelves stretching on in every direction, stacks on top of stacks. Every book has a black cover with no title. Masses of ghosts move through the stacks, rifling through books, ever searching for the knowledge they sought whilst living.

Oghma Infinium
Hermaeus Mora is associated with the ancient tome of knowledge, Oghma Infinium. Written by Xarxes, the scribe of Auri-El, the knowledge inside was granted from none other than Hermaeus Mora. The knowledge was then in turn passed over to Mehrunes Dagon, and was used to write the Mysterium Xarxes.

Summoning
The Eternal Champion, back in the time of Jagar Tharn was able to retrieve the Oghma Infinium in the deep frozen wastes of Skyrim; at that time Hermaues Mora did not interfere. Then the Hero of Daggerfall is recorded as the wielder of the tome, sometime.

The summoning date of Hermaeus Mora is 5th of First Seed. The Hero of Daggerfall quested for the Oghma Infinium by summoning Hermaeus Mora.

Hermaeus Mora's Cyrodiilic Shrine is located on a remote plateau deep within the northwestern portion of the Jerall Mountains (possibly due to the fact he is within the Pantheon of Skyrim thus being closer to where he is worshiped). After following the path of requirement, the Champion of Cyrodiil was then able to summon Hermaeus Mora, and was asked to bring one soul of each of the sentient races of Tamriel, so that his followers were able to perform a divination. The Champion was then awarded the Oghma Infinium, furthering their journey on the true path.

Skyrim
Two hundred years after the Oblivion Crisis, the tome has once again become lost. Upon finding an ancient Elder Scroll within a Dwarven Ruin in Skyrim, the legendary Dragonborn hero returns to Septimus, a crazed mage who told the hero where to find the Elder Scroll during the Elder Scroll main quest line. This mage had given the hero a runed lexicon which was needed to unlock the container the Elder Scroll is in (while doing this, the lexicon also absorbs the infinite amount of unknowable information contained within the Elder Scroll). Upon returning the lexicon to Septimus, the mage uses it to discover the way to open an ancient dwarven vault. It turns out that Septimus is a follower of Mora, and had been told by the Daedric Prince that the vault contains an artifact of great knowledge and power. In order to open the vault, Septimus must have a sample of blood from all the races of elves, or "mer." This means the blood of an Altmer, a Dunmer, a Bosmer, an Orsimer, and a Falmer. This is part of the quest "Discerning the Transmundane".

Upon accepting the hunt for these samples of blood, the Dragonborn is contacted by Mora who appears to him/her in the form of a Wretched Abyss. Mora says that Septimus has been a useful tool, but his usefulness will have run out once the vault is open. To that end, Mora commands the hero to seek out the blood as requested by Septimus, but upon opening the dwarven vault, Mora dispatches the mage. After collecting the Oghma Infinium, Mora once again appears as a void in front of the hero to name him/her his new champion. As with previous incarnations of this tome, it functions as a super skill tome that greatly boosts the skill levels of all talents relating either to warriors, rogues, or mages.

Trivia

 * If  Dovahkiin  enters Mora's realm of Apocrypha after " Discerning the Transmundane " has been completed, Hermaeus Mora will address him as his "champion" and that the Oghma Infinium was just the begining.
 * Several aspects of Hermaeus Mora are highly evocative of elements present within Lovecraftian Horror; most notably, his tentacled form resembles various deities from Lovecraft's Cthulhu mythos.
 * In Skyrim, his book, the Oghma Infinium appears to be made out of the skins of men and mer, like the Necronomicon.
 * In the Dragonborn add-on his shape resembles strongly to Yog-Sothoth, the most important deity of Lovecraft's Cthulhu mythos, which appears in several of his tales and has a vital role in his gratest work:  the adventures of Randoph Carter.

Appearances

 * The Elder Scrolls: Arena
 * The Elder Scrolls II: Daggerfall
 * The Elder Scrolls IV: Oblivion
 * The Elder Scrolls V: Skyrim