Order of the Virtuous Blood (Quest)

After completion of the quest, the hero will become a faction member.

To start the quest, go to the Temple District of the Imperial City, with a fame rating of more than five; Ralsa Norvalo will confront the hero, and ask that the hero come to see her husband. Go to Seridur's house.

Walkthrough
Seridur tells you about his group of vampire hunters called the Order of the Virtuous Blood. Basically, they kill vampires to cleanse Cyrodiil. Their first target is Roland Jenseric, whom Seridur claims to have seen bite a woman at night. Go to Roland's house and read the letter sitting on the table. You'll find the table on the entry floor, to your left as you come in. It has candles on it, so you can't miss it. The letter is resting on top of a book on that table. It refers to a cabin in the forest, which is at Roland Jenseric's Cabin, so Roland must be there.

Head to Roland's cabin in eastern Cyrodiil, slightly less than halfway to Cheydinhal from Imperial City. Enter and confront Roland. You can either kill him outright for 250 gold or listen to his story. If you listen, he tells you that Seridur is in fact the vampire. He saw his girlfriend get attacked by Seridur, while she was out on a walk. Roland further refers you to Phintias at First Edition in the Imperial City Market District if you want further proof of Seridur's outings. Talking to Phintias reveals that Seridur had mentioned a cave, Memorial Cave, located southeast of Imperial City.

Go to Memorial Cave and fight your way through various vampires and their undead minions. You may face any number of beasts, but remember to collect all Vampire Dust that you can. Deep in the cave, you will confront Seridur. Kill him and take his dust. Return to Roland with the news and he will tell you to meet him back in the basement of Seridur's house.

Meet him back in Seridur's basement, where he will reward you with the Ring of Sunfire, which resists disease and reflects spells. Also, Roland promises to give you 250 gold per portion of Vampire Dust you give him (he'll only accept it if it's from a vampire you killed) from that point forward within the game (except if you duplicate Vampire Dust, which he will accept, allowing for a quick way to make money). He does accept Vampire Dust collected before the undertaking of this quest.

You are now a "Brother" or "Sister" member of the faction.

Bug

 * If you get your information from Ralsa Norvalo whilst inside her house, it is possible to get locked in! If you do and you are a PC user, press "~" to open the console (see cheats), select the locked door, and type "unlock". Then press "~" again to close the console. Then restart the game and things should be as normal.