Bloodline

It serves as the third quest in the main storyline. Optionally, the Dragonborn may choose the option of learning the Vampire Lord ability.

Background
''While exploring Dimhollow Crypt, I freed a mysterious young woman named Serana from an ancient sarcophagus. She asked me to guide her home, to a castle off the northern coast of Skyrim.''

Escape
After speaking to the mysterious woman, it is revealed her name is Serana. She seems puzzled at her newfound freedom and asks to be accompanied to her home, Castle Volkihar, located west of Solitude.

Proceed to the exit on the far side on the cavern. Two Gargoyle statues will shatter and come to life. After defeating the gargoyles, proceed out of the cavern into the next room. There is a lever on the right that then opens a gate on the left.

Through this gate is a large arena of sorts. Several skeletons and a level Draugr or Dragon Priest will be seated in various places around the arena. A word wall is located on the far right where the first word of Drain Vitality can be learned. Around this room are at least four Malachite Ore Veins.

Proceeding through the final iron door, another gate can be found with a chain that leads to the exit.

Castle Volkihar
Upon arriving at Volkihar Castle, Serana is met with a grandiose welcome back, only to be cut short by her father, Lord Harkon, who only seems interested in the Elder Scroll that is on Serana's person. He then proceeds to question her on the "guest" she had brought with her. She reveals the Dragonborn had saved her from her entrapment. In a display of gratitude, Lord Harkon offers to bestow the power of a Vampire Lord unto the Dragonborn. He demonstrates this immense power by transforming into a Vampire Lord himself.

Good or evil?
The Dragonborn can either refuse or accept his offer:

Bugs

 * Sometimes the gate to Castle does not open after the gate keeper says his line. This can occur if Castle Volkihar is discovered beforehand, although this is not proven, nor has this yet been adressed by Bethesda.


 * Accepting the "gift" can cause the game to load last the save.
 * After accepting the gift, then changing to the Vampire Lord form, and then changing back to his/her normal form, the player may be wearing the clothes he/she wore before he/she changed to the Vampire Lord form and the clothes he/she was wearing while creating a previous save.