The King Vampire was significantly more powerful than the other vampires. As with all vampires, his heart needed to be destroyed completely for him to die. The King needed blood as his primary food source. (TV: State of Decay)
The Yssgaroth waged a great war against the Time Lords, who defeated them all with Bowships created on the orders of Rassilon. Only the swarm-leader survived. (PROSE: Interference) He travelled into E-Space, pulling the human spacecraft the Hydrax there as well.
The ship landed on a planet where it became castle-like in appearance over time. A community grew around it. Three humans from the Hydrax were made Vampires to serve the King, and were called Aukon, Zargo, and Camilla: the "Three Who Rule". Peasants were selected to be fed to the King Vampire, including Karl, son of the head villager Ivo. The fuel tanks of the Hydrax were filled with blood, which was fed to the King through tubing. He lay dormant under the ship for a thousand years, growing in power.
When the Time of Arising came, the King Vampire rose from the ground. The Fourth Doctor launched a scout ship from the Hydrax. The steel hull pierced the King's heart as it descended. (TV: State of Decay)