The Hierophant was a vampire and a member of the Vampire King's court.
Marceline fought The Hierophant centuries ago when she was on a mission to protect the remaining humans from vampires. When the vampires attacked the humans' ship, The Hierophant avoided the initial fight by disguising himself asSchwabl until Two Bread Tom noticed the dog was wearing boots. Marceline manages to defeat him and gain his shapeshifting powers.
The vampires are resurrected after Princess Bubblegum removes Marceline's vampire essence from her. After a short period, the Vampire King and his court manifest. The Hierophant advocates for a return to traditional vampire ways, suggesting that trying to adapt lead to their downfall originally. When the Vampire King admonsihes him, The Hierophant parts ways with the group. He seeks out Marceline in hopes of joining forces to bring down the king.
As a vampire with magical powers, Hierophant has the ability to shapeshift any part of his body at will. This can be seen in "May I Come In?", when he tries to subdue Marceline.
Against Sora's Team Edit
Once Master Xehanort resurrected the vampires by using a device to scan Marceline and revive the Vampires; they became twice as stronger, and became major threats than before.