Primum Dominum

 was a vampire. With the invulnerability granted by the Gem of Amara, he concealed himself as a human, adopting the alias Masters as the principal of Cleveland West Middle School.

Biography
As he was orchestrating a vampire attack at the school during an upcoming eclipse, a number of vampires began arriving in town. This called the attention of the Scooby Gang, who then began investigating Primum Dominum. Meanwhile, as the school principal, Masters would always support inappropriate behavior, such as when Buffy Summers accidentally hurted a colleague during physical education class.

When the Slayer identified Principal Masters as the Big Bad, he disappeared in vacation, returning only in the day of the eclipse. While the group of friends got to prevent the massacre, dispersing the students and fighting the vampires, Miss Sparks removed Primum Dominum's ring, leaving him vulnerable without the Gem of Amara, so Buffy staked finally him.

Appearances

 * "New School Nightmare"