Kill the leader of Pinemoon Cave

Walkthrough
The Solitude court mage, Sybille Stentor has a particular hatred for vampires. Ironic since she is apparently a vampire herself.

If the Dragonborn asks if there is anything to do for her (after Tending the Flames), Sybille will think up some menial task for the Dragonborn: kill the leader of the vampires in Pinemoon Cave. But she does not think the Dragonborn is intelligent enough for the clever vampires and anticipates failure.

Alternatively, the Companions might decide that there are too many blood-suckers in Haafingar.

Kill the leader of Pinemoon Cave
Head for Pinemoon Cave and wipe out the vampire leader.

Tell Sybille Stentor the vampire is dead
Return to Sybille Stentor with the news.

Töte den Anführer in der Kiefernmondhöhle