Zagreus is an invisible ape that John meets in Bumby as a part of his Taranushi. He originally introduces himself as Cornelius, of the same name of the character from Planet of the Apes. Zagreus is actually a jinx (someone who does not make a proper reincarnation and can cause great havoc around them) and remembers little about how he became what he is now. John decides to take him back to see his Uncle Nimrod, who may be able to break the spell.
Afterwards, he accompanies them Morroco because of Nimrod's reasoning that it is best that he stays with them. He is known too have the effect of making people forget things such as when he makes John forget his focus word. To prevent this, Nimrod cast a temprorary binding on him to prevent him from causing bad luck. He seems to be the only one to enjoy the El Moania hotel as he is able to watch local belly dancing shows on TV.
Zaregus stated that he had felt right at home here, and immediately began to grow larger and his former white hair began to grow darker. He began to adopt a new identity as a bigfoot or a sasaquash due to his large 10 foot stature. He said he enjoyed this because people would think he didn't exsist and legendary.
It was he who startled Mr. Groanin during the night, though they didn't recognize eachother at first. When he gets attacked by a bear, Zaregus brings him back to camp, where he was to be buried.