To access this quest, the previous quest, Denstadt's Catacombs, must be completed.
Nergal poisoned the soldiers and turned them into the undead. The group's leader slayed Nergal and his men, though Kieran suggests going deeper into the catacombs, to find if someone escaped. Through the underground complex, the group meets up with Farhang. The group's leader remembers he was not a vampire when he left Al-Betyl, and is now an ambitious Death Knight. Though Farhang does not recognize the group's leader, he still ordered others to attack.
Vampires have a lot of hit points and even Life Drain ability, which makes the battle against the death knight tougher than usual.