Dragon Quest VIII: Sora to Umi to Daichi to Norowareshi Himegimi

The court jester Dhoulmagus of the kingdom of Trodain stole a powerful magical scepter sealed beneath the royal castle. Using the power of the scepter, Dhoulmagus destroyed the castle, placed a curse upon the kingdom and its people, and turned King Trode into a troll and the princess into a horse. A sole surviving castle guard journeys with the king, the princess, a reformed bandit named Yangus and a few other companions in search of the evil jester and a way to break the curse.