Muthsera,
The School of Julianos, as the keepers of the Elder Scrolls and the Imperial Library itself, was asked not too long ago for information on necromancy, its deities and beliefs. I shall recreate http://www.gamesas.com/bgsforums/index.php?showtopic=802804&st=0&p=11670793&hl# for you below. I hope it helps.
Yours in the Scrolls,
___The Word Merchant of Julianos
Muthsera Vivra Omisran Akathon,
In the name of JHUNAL and all the Divines, welcome to the lore forum. May your time here be well spent in conversation and exploration of the obtuse and sublime.
With that being said, I shall attempt to answer your queries to the best of the ability given to me by my Lord Julianos (blessed be His holy name!).
The god of the necromancers is Mannimarco, known in his mortal life as the "King of Worms", although he is called the "God of Worms" post-apotheosis. His worshipers, known as "Anchorites", band together in the Order of the Black Worm. Mannimarco the god sends a message to his followers in Necromancer's Moon. The epic poem "Mannimarco, King of Worms" by Horicles sheds more light on this mysterious figure. Mannimarco's cosmic enemy is the Divine Arkay, described in the King of Worms' book Arkay The Enemy.
The capturing of "black souls" is a necromantic practice that can be explored in Souls, Black and White, and the instructions on how to create a "black soul gem" is detailed in an Anchorite's Note.
The necromancer Falcar's hastily scrawled note contains locations of altars that can be used to create black soul gems. Found during the Mages Guild quest "Necromancer's Moon".
Ancestors and the Dunmer is a kind of pamphlet describing the Dunmeri religion.
The Doors of the Spirit is a semi-religious text focusing on the tradition of the Dunmer- ancestor worship. This book discusses the ways in which spirits, or ancestors, are all around us and how they should be cared for.
On the Preparation of The Corpse details the proper way to create undead minions.
The Book of Life and Services allows one to recite a chant to the Skeletons in the game to make them fight for oneself.
An anonymous author wrote Legions of the Dead, a scholarly work about the Undead. Significantly less sketchy than most other books on this topic.
Blasphemous Revenants demonstrate the Dunmer point of view about summoning the dead.
Opusculus Lamae Bal ta Mezzamortie - Vampire lore - their creation, and the origin of the Lamae Bal, the Blood Matron.
The Tome of Unlife is a book belonging to Lorgren Benirus, a man seeking lichdom.
The Black Arts On Trial by Arch-Mage Hannibal Traven is a summary of a debate about necromancy.
Manifesto Cyrodiil Vampyrum is information about the Vampires of Cyrodiil.
Immortal Blood is a fictitious tale about a vampire hunter who likes to surprise his enemies by striking the first blow. Nothing seems to take him by surprise. Well... Almost.
Greywyn's Journal details the conflicts between vampire and Dark Brotherhood.
Journal of the Lord Lovidicus, who is Agronak Gro-Malog's father, Arena Grand Champion. This journal proves that Vampires are fertile. Found during the Miscellaneous quest "Origin Of The Gray Prince".
Lord Jaren's Journal details what happened to Lord Kain at the hands of a lich.
The Path of Transcendence is by Celedaen, a member of Mages Guild who practiced Necromancy to gain lichdom.
Scrap from Lorgren's Diary, who is the ancient Necromancer of Anvil.
A note describing a vampire's dislike of garlic is Vicente's Note to Ocheeva.
A Worn, Faded Note is found on the corpse of the Vampire Ghola gro-Muzgol.
Vampires of the Iliac Bay is self-explanatory.
Serjo, this is my submission to you up to this point. It is possible that I have missed a few texts along the way, however I, in good faith, believe that Julianos will direct us further if need be. Feel free to submit any further queries to the Chapel of Julianos Correspondence and Intake Department. (Ask for the Word Merchant...tell them I sent you.)
I hope this message finds you well. Keep the Empire and Law in your heart and mind always, and remember to Walk Always In The Steps of The Divine.
Yours in the Scrolls,
___The Word Merchant of Julianos