Orlak

Orlak was a powerful vampire that ruled Westgate.

History
Before the Dale Reckoning, Orlak was a powerful vampire and in -286 DR he proclaimed himself Night King and seized the city of Westgate; Orlak ruled for a century until the adventurer paladin Gen Soleilon defeated the master vampire and stopped his reign. Considered dead, Orlak became the ruler of the underdark of the city. Finally in 1370 DR, Orlak vampirized one of the clones of Manshoon just at the start of the Manshoon Wars.

In this first act the Manshoon's vampire clone searched and destroyed his sire, putting a end of the undead life of Orlak.

Behind the Scenes
It's not really clear if was the same Orlak in -286 and 1370