A character in C.S. Lewis' book Prince Caspian, one of The Chronicles of Narnia.
Doctor Cornelius was a half-dwarf who masqueraded as a human in Narnia after the Telmarines drove the dwarves and Talking Beasts into hiding. Fortune led him into service as young Prince Caspian's tutor. Doctor Cornelius taught Caspian the true history of Narnia which had been suppressed by Caspian's uncle King Miraz.
A magician of modest talent, Doctor Cornelius found the 1000 year-old enchanted horn of Queen Susan. He gave it to Caspian when he helped him escape from Miraz; when the horn was finally blown Susan and her siblings, the four ancient monarchs of Narnia, were summoned from our world.
After Miraz' defeat Doctor Cornelius became one of Caspian's most trusted advisors.