When you fought the last boss did you fight Yegerna on her own or Yegerna & Behrlihn, if you just fought Yegerna then you sided with Bellegar if you fought both you sided with Behrlihn. When you get down to the area where you find Rhode after you've finished the puzzles & are arout to free Behrlihn Balleger appears & give's you one final chance to save the world. He offers to give you what you need to save Alaroth if you leave Behrlihn were he is. If you agree then you side with Bellegar if you don't then you side with Behrlihn, but it's that choice that dictates the ending.
