The final battle is a easy one, which was a disappointment. Well, it was easy for me since i was level 79 (immortals). You cant use your mortals in the fight, but they do help out, all 5 mortals cast a different spell to aid you in the first of the last 2 battles. In the very last battle, all you gotta do is take around 50k hp from him, but dont waste your time casting Buff spells (spells that add strengths to your party like barricade, or powerus type spells) so just stick to damage dealers. I would suggest casting double-leveler with sarah and ming, and attacking normally with kaim and seth. OR you could attack with kaim and seth, and cast Zephyrus-Divide (not the other way around, make zephyrus first) with both sarah and ming. The reason you cast zephyrus first is because it will allow you to cast divide without waiting a turn. Double-cast skill is needed of course. When the battle is over, there is like 15 minutes of cutscenes. I wont spoil it here, but it is a great ending. When the credits come, skip em, youll get the achievement, and youll be asked to save your game. SAVE! it will allow you to start a new game from disk one (on the save that your using) with level 50 characters, but nothing else. This is extremely helpful, especially if your gunna run through a second time in order to get the treasure trove. Refer to my treasure trove solution for help. If you need a step by step guide to treasure trove instead of just a list of items in each area, go to gamefaqs, and find lost odyssey, then read Split Infinity's lost odyssey guide. Follow it by the letter and youll get the treasure trove achievement.