Transformations?
I'm not sure if it's this movie or another centered around Atlantis - the basic plot of this sounds similar to the one I'm thinking of.
The Atlantis movie I'm thinking of has the main character being prepared to be transformed into a beast - the villain taunts him with what kind of beast he will be, whether a mule or pig etc. He also mentions that unlike most of the people turned into beasts the hero will retain his memory. A friend of the hero is undergoing a transformation into a minotaur'ish character, you see him over time as the transformation becomes more pronounced.
In the end the island is destroyed and the hero escapes unharmed.
Is that this movie or a different Atlantis movie?