Hermaeus Mora

"I am Hermaeus Mora, I am the guardian of the unseen, and the knower of the unknown.""

- Hermaeus Mora (Skyrim)

Hermaeus Mora is a recurring character in the Elder Scrolls series. He's known by the mortals denizens of Tamriel as the Daedric Prince of Knowledge. His sphere is the scrying of the tides of fate, of the past and the future. Mora's plane of Oblivion is called "Apocrypha", which is an endless library full of forbidden knowledge, teeming with ghosts that are afflicted with a thirst for knowledge that they sought when they were among the ranks of the living.

The artifact that Mora bestows upon his champions is called "The Oghma Infinium", which is a powerful tome of knowledge that was written by Xarxes, a god of secret knowledge and ancestry

Elder Scrolls IV: Oblivion
In the Elder Scrolls IV: Oblivion, Hermaeus Mora has a shrine,which is a statue depicting a large mass of tendrils and eyeballs. Mora's Daedric Quest in Oblivion involves capturing souls from each of the ten races. Once the quest is completed, the player is rewarded the Oghma Infinium.

Elder Scrolls V: Skyrim
Hermaeus Mora's Daedric Quest in Skyrim is called "Discerning the Transmundane", and it's intertwined with the main questline.

After the Dragonborn inscribes a Dwemer Lexicon for Septimus Signus, an elderly mage who lost his mind from isolation, Septimus takes the Lexicon, and gives the Dragonborn a device meant for gathering the blood of Mer (elves), called an "Essence Extractor". Just as the Dragonborn is about to exit Septimus's lair, Hermaeus Mora himself appears before them as a void of darkness. Mora tells the Dragonborn that Septimus will have outlived his usefulness by the time he opens the Dwemer Lockbox that the Oghma Infinium is stored in. Mora disappears, and allows the Dragonborn to exit Septimus's hideout.

After the Dovahkiin collects all of the blood samples that Septimus requires, the latter uses the samples to open the Dwemer Lockbox. To Septimus's dismay, the "heart of a god" that he seeked within the lockbox is not present, only the Oghma Infinium. Suddenly, Septimus is disintegrated by Hermaeus Mora, and the Dragonborn is allowed access to the Oghma Infinium, and they are given the title of Mora's Champion.

Elder Scrolls V: Dragonborn
After reading one of Mora's Black Books that was stored in a Dwemer Ruin called "Nchardak", the Dovahkiin meets Hermaeus Mora in person, rather than just as a void, as he appeared in "Discerning the Transmundane". Hermaeus Mora gave the Dragonborn the second word of power to the "Bend Will" shout for free. The third word of power would be given to the Dragonborn, as long as the latter forced the Skaal shaman, Storn, to give up all of his wisdom to Mora. After Storn's death, the Dragonborn travels to Apocrypha, now with the entire Bend Will shout. During the battle between Miraak and the Last Dragonborn, Hermaeus Mora intervened and impaled Miraak with one of his tendrils. Mora killed one of his champions because he knew that Miraak was planning to betray him eventually. After Miraak's demise, Mora dubs the Last Dragonborn to be his true champion.

Personality
Despite being the most monstrous and inhuman out of many of the Daedric princes, Hermaeus Mora is very polite and affable. He's also quite generous, as he happily gave the Dragonborn the words of power to the "Bend Will" shout, which is one of the most helpful shouts in the game.

Hermaeus Mora may be very polite and generous, but he does indeed has a bad side. If you try to hide knowledge from Hermaeus Mora, he will go from pleasant and friendly, to violently angry and homicidal in a matter of seconds. This was demonstrated in ES V: Dragonborn, where Storn and Miraak were impaled by Hermaeus Mora for attempting to hide knowledge and wisdom from him.

Daggerfall/Oblivion
Hermaeus Mora is depicted in Daggerfall and Oblivion as a mass of green tentacles, claws, and eyeballs amalgamated into one being. The giant crab-pincers that stuck out from his body were the most prominent features about him.

Skyrim
Mora's appearance in Skyrim changed very drastically from his older counterparts. In Skyrim, Hermaeus Mora is a mass of black tentacles, a single large eyeball, and black smog.

Quotes
"At last, the Skaal yield up their secrets... TO ME!"

- Hermaeus Mora after learning the Skaal's secrets.

"Did you think, you could escape me Miraak? You can hide NOTHING from me here!"

- Hermaeus Mora after impaling Miraak

"Your free will is an illusion. Whether you acknowledge me or not is your own business, but I will be in your mind..."

- Hermaeus Mora

"As I told you when I gave you the Oghma Infinium, your free will is an illusion. Why else would you be here?"

- Hermaeus Mora

Trivia

 * In Skyrim, Mora was voiced by Wes Johnson, who was the voice actor of Sheogorath in The Elder Scrolls IV: Oblivion.