Alright, I give you Heravix of Gaul!
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Name: Heravix of Gaul
Age: around 2200, no one knows exactly
Species: Lich
Appearance: A very slender and tall man wrapped and covered in black, grey and blue shreds of cloth that constantly shift and move. His face is long and pale, he has long silver grey hair that flows from his head as well as his chin. His eyes are glowing blue. He never opens his mouth when he speaks, instead he uses magic. His hollow voice always seems to echo from everywhere in the room. The cloth goes all the way to the ground, you never see his feet stick out from under the robe as he seems to glide as he moves.
Powers:
Wide array of spells, incantations and rituals.
Immortality. (There's a magic object called a Phylactery that contains Heravix's soul. As long as it's safe he is immortal, his body will regrow near the Phylactery in a week if he is destroyed.)
Classes(In Order, Max = 8): 
Teaches Mythology and History
Is student counselor
Personality: Think of the warmest, nicest, most caring person you know. Now stick that person in a freezer and hide him/her on the Antarctic for thousands of years.
History: In days before days forgotten. In times before the rise of the roman empire. There lived a man in what we now call France. He still lives. He found a way to store his soul and bind himself to the material world. No one but him knows more about his history than this, and even he doesn't remember much.
Crush/Relationship: Not that anyone knows of.
Family: Not that anyone knows of.
Friends: The other staff of the school sort of like him, once they get to know him. The same goes for many students.
Other: Heravix is a relic from different times, he has completed all of his goals a long long time ago. He took up teaching out of boredom a couple of hundred years ago and stuck to it ever since. He takes an interest in the lives of the students because "youth is creative" and he loves the rare moments he can be surprised.
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Like?
Now, I know he's a tad powerful. But since he won't really meddle with affairs other than give advice and such. It shouldn't be an issue. 
His role in the story should be kind of like that of Tom Bombadil.