Original: The remaining party then goes to Tethe 'alla to find answers, where their goal ultimately changes from saving Sylvarant to saving the two worlds without the sacrifice of the chosens life. In order to do this, they decide that they must sever the ties between Sylvarant and Tethe' alla to separate the worlds, thus ending the competition for mana.
Simplified: They go to a different world called Tethe 'alla.