Other than for a challenge (to try to beat Klauth at full HP), is there any reason to use the Full Dragon Sphere instead of the Dead Dragon Sphere?
Do you get a bigger reward (experience, gold, items, etc)?
What about keeping the Full or Dead or vanilla Dragon Sphere (or not even bothering with picking up the Dragon Sphere)? Is there a use for them later? Or will they be removed from inventory upon completion of Chapter 3?