The High Priest

When the Priest turns into an animal, he leaves his boots behind, which may be a reference to the story "Puss in Boots."
Basically, he transforms into animals of certain species, highlighting their menace. For example, the large cat/fox he transformed into clearly displays demonic features, resembling the artistic style of 17th-century grimoires such as the demons of the "Goetia" from the "Lemegeton".Its style resembles the image of a Russian devil from 19th-century fairy tales: a sheepskin coat, boots, small horns on the head, a long tail, donkey ears, and a beard.

Like most vampires, he will die from direct exposure to sunlight or a stake through the heart. Since he is a vampire who lives by outdated principles, he is unable to enter a house unless he is invited, and if he does, he will die

Physical Form Change: The High Priest is able to change his form or the form of his body parts at will. This ability was demonstrated in the episode "Can I Come In?". He is also able to produce poison, similar to the poisonous animal he transforms into. Additionally, he is capable of enhancing his sense of smell, vision, or hearing, as well as flying (by transforming into a creature with wings).
Skills
Playing the balalaika: He can play the balalaika, as shown in the episode Vampire Business.

Marceline fought the High Priest many hundreds of years ago when she was on a mission to save the human race from the vampires. When the vampires attacked the human ship, the Priest disguised himself as Marceline's dog, Shwabla. Two Bread Tom noticed him because of his boots. In the battle, Marceline managed to defeat him and obtain his shapeshifting abilities.
The Priest is resurrected when Princess Bubblegum accidentally releases the contents of the vampire essence she extracted from Marceline. During a vampire council, the High Priest advocates for the return of old traditions, as adapting risks the vampires' extinction. Opinions are divided, and the High Priest leaves the group.
He goes to find Marceline, and he catches and interrogates King Uuu and Chickle, who tell him that Marceline is staying at the Princess Bubblegum's hut. At Gumbald's hut, he finds Minty the Footman. The Priest stands on the doorstep of the hut and forces the Footman to tell him where Marceline has gone, but the Footman only mocks him, calling him stupid because he cannot enter the house until he is invited.
He finds Marceline by her tracks and her scent, and he offers her to join forces against the King in order to overthrow him. Finn, Marceline Gum and PPK hide in Jake, which has become a cabin. Marceline refuses his offer and a battle ensues.
As a result, the Priest stung Marceline with the scorpion's venomous tail, but Chicle pushed it into Jake's house and the Priest died," entering the house without permission " and breaking his rule.

The High Priest (English: The Hierophant) was a vampire at the court of the King of Vampires.