Zagato was the High Priest to Princess Emeraude and Clef's right-hand man. When Hikaru, Umi and Fuu arrive at Cephiro, they're told that Zagato has captured Princess Emeraude and now their world is crulbling without its pillar. Zagato acts like a cold hearted man who will do anything to achieve his goal, indifferent to the chaos in Cephiro. However, his true purpose remains obscure untill the girls fight him.
It's later revealed that he and Emeraude were in love, wich caused the unbalance in Cephiro. He had imprisioned Emeraude to prevent her from being killed by the girls, according to the profecy.