Oblivion Remastered: Dark Brotherhood – Darkness Eternal Guide
Darkness Eternal allows players to become a Vampire in Oblivion Remastered through the Dark Brotherhood. Learn how to receive Vicente Valtieri's Dark Gift, and embrace it. Also learn how begin the Vampire Cure quest if you decide to reverse the transformation.
How to become a Vampire through the Dark Brotherhood.
Walkthrough
Talk with Vicente Valtieri

After completing “The Assassinated Man,” Vicente Valtieri will offer the Hero “The Dark Gift.” He will explain the process. The Hero needs to go to sleep. Vicente Valtieri will come to them and administer the bite. This will infect the Hero with Porphyric Hemophilia.

- This infection will bypass any disease resistance that the Hero has.
Sleeping Without Leveling Up
There is at least 1 bed you can use to sleep without triggering the Level Up prompt (if you’re trying to avoid it). You need to head for the Inn of Ill Omens. This Inn is found

Spend the 10 Gold for a bed. Take the stairs on up and go into the first room on the left. Sleep on the mat in there. You will get the triggers for having gone to sleep without triggering the Level Up Screen.
Become a Vampire
Once the Hero has Porphyric Hemophilia, the waiting begins. It takes 3 days for the disease to advance into Vampirism. At this point, you will need to sleep again for the final step to complete. Once you do, Porphyric Hemophilia will become Vampirism.

Getting More Information on Vampirism
After becoming a Vampire, you can return and talk with Vicente Valtieri. You will have a new dialogue option: Curing Vampirism.
Curing Vampirism
To cure yourself of Vampirism is a long quest called “Vampire Cure” that you can get from Raminus Polus at the Arcane University in the Imperial City.