|Discerning the Transmundane|
|Septimus Signus's Outpost|
Tower of Mzark
This quest begins by reading the book Ruminations on the Elder Scrolls.
Ask Urag about the insane book
This step may be skipped entirely.
Find Septimus Signus
When the Dragonborn finds Septimus Signus's Outpost, the mad scholar living there asks for help opening the strange Dwemer box inside. To do so, Septimus must use an Elder Scroll which requires a lexicon to be transcribed.
Transcribe the Lexicon
This transcription can only be done at a Dwemer Oculory located within the Tower of Mzark in Blackreach, and the only way to reach the tower is go through Alftand, then Blackreach. This is easily the longest and most fraught part of the quest as both Alftand and Blackreach are extensive and certainly not lacking in Falmer and other dangerous foes.
Once inside the Tower of Mzark, the Lexicon must be placed in the receptacle, and the Oculory must be activated using the four buttons on the platform above the Oculory. Once done, the Oculory will reveal an Elder Scroll and the lexicon will have been transformed into a Runed Lexicon.
Note: Be sure to take the Elder Scroll! Do not leave it behind and it is a long way to go to retrieve it.
Give the Lexicon to Septimus / Return to Septimus
Return to Septimus' Outpost and give him the lexicon. This will reveal that he requires Dwemer blood, but since the Dwemer are extinct, he will need the blood of the five other elven races to make a facsimile.
Harvest the five types of blood
This part of the quest generally simply happens as part of combat during the general exploration of Skyrim. If the Dragonborn kills a suitable target (one each of the following races: High Elf, Wood Elf, Dark Elf, Falmer blood, Orc) and uses the Essence Extractor to get a blood sample for Septimus. A dialogue box is automatically presented when the Dragonborn loots a suitable corpse.
Bring blood to Septimus
Once you have all the blood samples, return to the Outpost and Septimus. Give him the blood samples which will allow him to finally open "the box". Inside is a pedestal with the Oghma Infinium. Septimus will rush over to the tome but as soon as he reads it, he will be reduced to a pile of ash.
Take the Oghma Infinium
Take the book and choose your path.
See the notes about the Oghma Infinium levelling exploit.