Sigma

A young wizard and the son of a prophet. He guided Arusu and her friends to the Wizard Kingdom in order to help Grande get the True Book of Spells from them. In the end, he was thrown in prison for his failure to bring the wizards the book and a witch they need to cast dark magic.

Sigma's father was killed by Grande when he tried to advise him not to use the forbidden dark magic because he foretold that a savior, Arusu, would come and save the world.

Later in the series, it was revealed that Sigma was actually working covertly against Grande in order to help his father's prophecy come true.
(Source: Wikipedia)