Eriol

Eriol, just Eriol, without a surname, is an half-elf, who was took under the wing of Iterator Entulentesë, Gamael's father and predecesor of Thedonia's duke.

Altought a man of limitless wit, his heritage (he was the fruit of the love of a man and an elf woman) cursed him making mostly an outcast, and giving him a shorter lifespan in a society that tooks centuries to make any advance.

An elf (or human) of his talent and will would be able to reach a high position on any conclave, but elves didn't want an outcast that "Only" would last for a century, and humans didn't want a leader that would last for too many generations. He, nevertheless, acquired the position of Master Librarian of the Enthulentesë family, and was a tutor on magic of the small kid of the family, Brendam; who he grew fond of a talent which mirrored his.

Maybe that Eriol discovered Brendam's secret, a secret that even the whole boy didn't know, and prepared him to live as an outcast, like himself had to live

Death
The old master meed his end when Nervus attacked Thedonia. Presumibly while the attack of a summoned T-Rex. Altough there were huge losses among the thedonians, the high nobility didn't miss him (calling him 'it', due his mixed blood)

This treatment of his mentor enraged Brendam, who remembered that Azrial's method included not only his vast powers, but also politic, ralling the opressed races. Maybe even his death was a lesson and a message for Brendam.