Discerning the Transmundane

Discerning the Transmundane is a quest in The Elder Scrolls V: Skyrim.

Overview

 * Prerequisites: None in order to start the quest, but Septimus will not decrypt the Lexicon until you have reached level 15.
 * Quest giver: Septimus Signus
 * Reward: Oghma Infinium
 * Reputation gain: N/A



Background
"I met Septimus Signus and brought him a dwarven lexicon containing the distilled knowledge of an Elder Scroll. With it, he believes he can open the lockbox he's been studying by creating a mixture of blood that will resemble dwarven. I need to collect blood from several different races if I want to help him."

Objectives

 * Ask Urag about the insane book
 * Find Septimus Signus
 * Transcribe the Lexicon
 * Give the Lexicon to Septimus
 * Harvest orc, falmer, dark elf, wood elf and high elf blood
 * Bring the blood to Septimus
 * Take the Oghma Infinium

Walkthrough
Ask Urag gro-Shub about the book. He'll tell you about a hermit, Septimus Signus who has devoted his life to The Elder Scrolls and holds a solid amount of knowledge on them. Travel to Septimus, who'll give you a Lexicon and sends you to Blackreach, an underground dwarven city, which you enter through Alftand.

At some point you will encounter a sphere which you will need to go through a puzzle where you need to push buttons in order to open. Activate the Lexicon Reptacle to the right of the buttons to gain access to the two buttons to the right. To decipher the code, press the second button from the right until the Lexicon opens and the third button lights up. Press the third button until you see the overhead lenses directing light onto the sphere, and the fourth button lights up. Press the last button and retrieve the scroll. Now pick up the transcribed Lexicon from the reptacle and then procceed to pick up the Elder Scroll.

Return to Septimus, who will now ask you to gather some blood in order to make a dwarven blood replica to open the door to the dwarven artifact in his outpost. You need to gather the blood of the following races: To harvest the blood, you need to loot the corpse of someone from each race. A good place to get this is Liar's Retreat, which has all of the blood types.
 * Orc
 * Falmer
 * Dark Elf
 * Wood Elf
 * High Elf

Bug (?) After returning the Lexicon, Septimus will not ask you to retreive the blood of each race. Will just be stuck in a loop (360)(PS3)

Hermaeus Mora's Intervention
Upon trying to leave the iceberg, Hermaeus Mora, Daedric Prince of the unknown, confronts you and tells you that you have been doing well. He tells you that as soon as the lock box is open, Septimus Signus's time will be over, and that the Dragonborn should take his place. You have the option to agree or disagree.

Disagree
You tell the wretched Abyss you will never be their servant, and its response is "you shall not evade me forever"; then it disappears.

Agree
He then asks you to speak with him once the box has been opened, and all will be revealed.

Either you agree to be his follower or not, this will not have any (at least not noticeable) consequences or diferences after finishing the quest.

Suggested Sources of Blood
The following are suggested sources of blood which you may turn to if you can't find any on your own.

The best place to gather blood would be at Liar's Retreat (lies south-south-west of Dragon Bridge) or at Chillwind Depths Just east of Liar's Retreat. The cave has many falmer and the corpses of all races. The easiest place to find a high elf is the corpse in the spear pit out the back entrance of Halted Stream Camp. Another good spot to find a high elf is north-west of Helgen. Between Pinewatch and Anise's Cabin you'll find a hostile Novice Conjurer, and a Shrine of Talos with a dead Thalmor wizard on the mountainside directly South of Anise's Cabin.

Alternatively you can obtain the high elf blood by traveling to Solitude, then give the store Radiant Raiment a tiny visit. This store is run by two high elves, Taarie and Endarie. You should kill Endarie as she doesn't provide you with any quests. Taarie will still be there to run the store selling the same items Endarie did.

The Thalmor Embassy is also a very good location to find several High Elves. You can lock pick your way into the guard barracks and harvest the blood of an unsuspecting sleeper. (When I played through the mission 'Diplomatic Immunity', I found High Elf, Wood Elf, and Dark Elf blood.)

An even better source of High Elf blood is at Northwatch Keep, along the shoreline Northeast of Mor Khazgur or Northwest of Volskygge.

High Elf and Dark Elf Blood can be found at Cragwallow Slope, which is slightly southeast of Kynesgrove. It is a cavern filled with elven Conjurers, so at least one of the two types of required Elf blood can be found here.

If you don't feel like killing off named NPCs or are trying to avoid criminal acts, hostile high elves can also be found at Uttering Hills Cave in the form of the Summerset Shadows or at the Thalmor Embassy.

A hostile Wood Elf can normally be found among the bandits at Silent Moons Camp. There is a Wood Elf in Riverwood named Faendal who can be used for blood. Note: Doing this will not allow you to complete his associated quests.

Two other Wood Elves can be found in Whiterun and are the owners of The Drunken Huntsman. They are Anoriath and Elrindir. Attacking them can lead to the guards being called. There is also a Wood elf corpse in Sunderstone Gorge next to the Word of Power for Fire Breath

If for some reason the "Dark Elf" was not in Liars Retreat (as stated above) then go to Riften. There is a Dark Elf in the market district that is female. She sells Harvested goods so just take her out, then pay off the guard 350 gold and you're on your way.

Video Guide
http://www.youtube.com/watch?v=yVCBICPy71Q

Quest Conclusion
After you've gathered the blood, return to Septimus. He will open the dwemer box using the blood you gathered but as he enters inside and finds the pedestal on which the Oghma Infinium resides he is killed by Hermaeus Mora by suddenly disintegratrating him into a pile of ash.

Bug (?): When Septimus finds the book, Hermaeus Mora might not kill him and the quest will get stuck. However, you can just kill Septimus yourself and the quest will then continue as it should. (PC)

Step inside and take the book. As you leave the chamber the Wrectched Abyss appears again as a manifestation of Hermaeus Mora. You can decide to work together with him as his Champion or to disagree with any of his plans. This choice doesn't affect your actions in any way.