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i believe there are two world the one everyone is living on and the shadow world
and i think that if they dont solve the quest the shadow world will get bigger till it will no longer be in the shadow but all the monsters just like the dragon will apear in the real world
if i am wrong do correct me (=・ω・=)
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I believe it's as you said. The shadow worlds used on tests are the ones previously vanquished, hence Desir knowledge on the composition and objectives of it is so overpowering.
One might think they're playing around just completing quests, but that's only because Desir forced the party to study history to learn about the SW and how they were vanquished.
You can think of these tests as pretty hardcore history lessons where they actually get to experience the past on first person perspective.
I don't understand the part that someone needs to fulfill the quest. I understand that they need to get stronger to protect their world but to fulfill the quest makes me mad. What is the used of completing those quest? Where you can just jump on the teleportation to fight those dark shadows, kill the beast, gettting the gems and cultuvating those mana inside it be become the strongest. I feel bad for quest. Was it just a test or a computer simulation? Help me to clear this thougths.