Nicodemus is the Headmaster of Spirit High. He is very mysterious, as no one knows for sure who he is or where he comes from.
Nicodemus have lived for centuries, and had grown bored. Observing all the violence concerning supernatural creatures -- both for and against -- Nicodemus decided to start a school. He found an abandoned castle, and transformed it into the boarding school we see today.
No one knows what Nicodemus is. Is he a demon? A spirit? Some sort of rat-man?
The only confirmed thing about Nicodemus is that he is a shapeshifter. His other form is a great owl, with the same strange glowing eyes.
Nicodemus is also immortal from natural death. Age and disease with not kill him, murder and accidents can.