Hermaeus Mora

Hermaeus (or Hoermius or Hormaius or Herma) Mora, whose sphere is scrying of the tides of fate, of the past and future as read in the stars and heaven, and in whose dominion are the treasures of knowledge and memory.

Herma-Mora (The Woodland Man): Ancient Atmoran demon who, at one time, nearly seduced the Nords into becoming Aldmer. Most Ysgramor myths are about escaping the wiles of old Herma-Mora. Also called the Demon of Knowledge, he is vaguely related to the cult origins of the Morag Tong ('Foresters Guild'), if only by association with his brother/sister, Mephala. (Varieties of Faith in the Empire)

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, shelves stretching on every direction, stacks on top of stacks. Pages floated on a mystical wind that he could not feel. Every book had a black cover with no title. Masses of ghosts moving through the stacks, rifling through books, ever searching.

The summoning date of Hermaeus Mora is 5th of First Seed.

Hermaeus Mora is always associated with the Oghma Infinium, a tome of power that can increase the attributes of the reader instantly. The knowledge given by Hermaeus Mora himself was penned in the tome by the Ageless One, the wizard-sage Xarses.

This obscured Daedric Prince sometime cannot be summoned as "easily" as other Daedric Princes. During the Oblivion Crisis, after the Champion of Cyrodiil finished all the quests from other Daedric Princes, the Champion of Cyrodiil was summoned instead of the champion summoned the Prince. Hermaeus Mora asked the champion to get souls, one of each of the sentient races. An evil contract, the champion finished the contract anyway. Hermaeus Mora then rewarded the champion the Oghma Infinium.

The Eternal Champion, back in the time of Jagar Tharn was able to retrieve the tomb 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 after the War of Betony. The hero summoned Hermaeus Mora, and he was asked to slay certain patrician who had aroused Daedric Prince's displeasure. Upon finishing the quest, the Hero of Daggerfall was rewarded with the legendary tome.

copied from http://www.imperial-library.info/book_daedra/