Grand High Vampire was the name given to the unnamed character with that title, played by Richard Elfyn He is generally portrayed as not being very nice, and pursuing the evil ways of vampires, however he pursues his duty of convincing Vladimir Dracula he is the Chosen One to the extent that he is willing to die for vampire honour.
When Vampires Go Bad
In "When Vampires Go Bad", the Grand High Vampire made his first proper appearance, played by Richard Elfyn, when he visited the Count at the castle in Stokely with Boris Dracula, who was at the time disguised as Justice Moroi. He came after many letters had been sent to him by Krone and Atilla Westenra, several guests at the Hunt Ball, and Boris Dracula, made allegations against Count Dracula to do with fratinising with breathers and slayers, which was ultimately meant to lead to the Count's execution.
However, he was then killed just before midnight, and after a lengthy investigation, it is revealed that it was in fact Boris Dracula, disguised as Justice Moroi, that did it.
The Chosen One
In "The Chosen One", the ghost of the Grand High Vampire comes back to haunt Vladimir Dracula, informing him that he must put on the Crown of Power and make take the title of Grand High Vampire because he is the Chosen One. He continually appears throughout the episode until Vlad finally agrees to put on the crown in order to save his father and sister. He states that: "You will know you are the Chosen One when you sacrifice the life you love to save the family you love."