Two year later after escaping Helgen and accepting to join the dark lord Xile, who said Saren was free to go on with his life and that the dark lord will summon him when the time was right, Saren spent the last two years doing mercenary work in Riften when one night he was approached by a unknown hooded figure on his way home.
He was given two packages and the hooded figure turned invisible and disappeared into the night. Saren arrived at his home called Lakeview Manor, where he later spent the rest of the night in the basement. He opened the first package which contained a black book but when he opened it revealing the pages to be blank as he flicked through each page until a small note fell out one of the pages.
He placed the book back down on the table, picking up the small folded note and proceeded to read its contents, the note stated that his service to the dark lord has come into effect and that his first task is to drink the potion that was given to him and that he will gain unimaginable power.
After drinking the blood potion, he started to feel faint then he collapsed onto the floor in a comatose like state. He later awoke to find himself in the hall of the dead in Whiterun, They already started to prepare his body by marking his torso with an embalming tool but they didn't remove his internal organs yet.
Saren noticed that his skin had become rather pale, he felt very weak and he was craving something but not for food but for blood. The potion must have transformed him into a vampire. Suddenly he heard some commotion at the end of the hall behind a wooden door maybe it enhanced his natural senses.
He sat there as he listened in on their conversation and when they were heading back to check on him, he quickly formulated a plan and decided to play dead and attack at the right moment, when the priest of Arkay leaned over his form with the embalming tool in hand while the other was turned around.
Slowly grabbing the steel dagger on his belt without him noticing, opening his eyes and quickly stabbed the dagger into the other priests abdomen and just as the other priest turned around he grabbed his throat and pierced his hand through the priests chest, the priests hood fell down and Saren tilted his head to the side before sinking his fangs into the mans neck draining him dry before pulling his heart out of his chest.
Blood dripping down his mouth as he loosened his grip on the mans limp body he turned his head to the side and proceeded to do the same to the other priest ripping out his heart and draining him dry of his blood. Saren body stopped craving blood, his features started to fill out, the scars on his body started to disappear as color returned to his pale skin.
He held one of the priests hearts above his head, he opened his mouth revealing a full set of sharp teeth and a long tongue and dropped the heart into his mouth devouring and repeating the same with the other heart feeling satisfied. He cleaned up the left over blood and bodies that were left behind by placing them in empty coffins as he avoided the shrine of Arkay in the room, he found some clothes and started placing them on his person before regaining his posture.
Pulling his hood over his head as he stepped outside into the harmful rays of the sunlight beaming down on his undead form, he raised his head, the lower part of his face came in contact with the sunlight, his exposed skin started going through the stages of first to fourth degree burns leaving a charred jaw, exposed teeth and burned away skin, he lowered his head, shielding his lower half of his face once more from the sun.
The lower half of his face started to regenerate slowly until it was completely healed, leaving no scars behind thanks to his supernatural abilities. He took refuge in the Drunken Huntsman Inn until the sun eventually disappeared. He wanted to wait for the moon to appear before setting off again, he had been drinking bottles of blood from his last victims until he needed to feed again.
Saren noticed that he no longer felt weak and while his hunger for blood stayed the same, he felt increasingly stronger when he had finished feeding on the two priests at the hall of the dead. He took a seat at the back of the room and opened the blank black book once more but this time the pages magically filled with writing. The first page had his name, number of victims killed, drained including the date when he transformed into a vampire '20th of Rain's Hand' and the current time and date
The next page showed requirements for Risen, he had to kill a certain amount of times and how much blood to drain then sleep for 24 hours to progress into the next stage. The rest of the pages contained information about vampirism, how to survive and what are the advantages and disadvantages along with new vampiric powers and abilities.