Auzou Unicorn quest book

Solvélig's destiny is set by his father: he will join the army of the King of Organd. But the boy is not a soldier at heart... He'd rather be in the service of animals, especially unicorns... They are hunted by mysterious hunters, who sell their horns as a cure for witchcraft. When Solvélig's path crosses that of Buronzan, a magnificent unicorn, his future is turned upside down. Together with the rebellious Lahima, they put their lives on the line to protect these magical creatures from the unicorn hunters, and the most terrifying of them all, the terrible Drogrel... But the enemy is not always who you think...