Juan Manuel de Ayala y Aranza is a Spanish ghost who resides on Alcatraz island. He is the original founder of the island, calling it "La Isla de Los Alcatraces" (Isle of the Pelicans) referring to the brown pelicans species native to San Francisco.
In the series he assists Perenelle Flamel while she is imprisoned in the prison on Alcatraz by scouting for danger. Juan is powerful enough to be considered a poltergeist, meaning he is able to alter his surroundings to some degree, which he uses to draw the Sphinx away from Perenelle so she can regenerate her aura. Unlike most people, Perenelle can see the ghost because she is the seventh daughter of a seventh daughter.