I always wondered why the status effect linked with Aura was poison. Then I realized that while Aura is the spirit of gold, it could also be said to represent metal in general, and with the sheer number of toxic metals in the world...
One of the recurring themes of all major story arcs is that Love Makes You Evil. This seems like a harsh common aesop through the stories but then you remember that, in the end, the Mana Goddess is love - seeing how the very essence of love itself was corrupted on this universe, no wonder these things are happening.
One of the themes in this game is You Can't Fight Fate. How does this get integrated into gameplay? Most of the time, intervening in the lives of others only results in a bigger pile of dead people, and even when you do make a difference, as soon as the mana tree is healed the Reset Button is mashed and you get kicked into New Game+ with everything undone and you have to watch the same tragedies happen over and over and over again. Welcome to Existential Despair: The Game.