The Crystal Saint is Cygnus Hyoga’s and Kraken Isaac’s master in the anime adaptation, as opposed to the manga, in which it is Aquarius Camus master. In the anime, Camus was Crystal Saint’s master.
In the anime, Hyoga’s master was the Crystal Saint, with Aquarius Camus being his master’s sensei (thus, making the gold saint the equivalent of an idol in Hyoga’s eyes). The Crystal Saint was a kind man, and his abilities hovered around silver saint level.
The Crystal Saint was first introduced in the Sanctuary arc, where he opposed Pope Ares’s actions against Saori Kido and her bronze saints. But before the Crystal Saint could speak out further, the Pope used his Emperor Demon Fist — a technique that forced the victim to obey him against his will.
The Crystal Saint was then sent to assassinate Hyoga. A battle ensued between teacher and student, with Hyoga reluctantly landing the final blow. The strike knocked the Crystal Saint out of Ares’s grasp, but proved fatal as well.