Humans have found the magical land that had just been a myth. They can learn all kind of magic, unimaginable to the human before them. Now they must live with other magical creature too, but they are not as intelligent as human expected.
Their goals are just living and preserving the land of theirs. Humans have a more devious plan, of course, to colonise and exploit the land for their own benefits. What they don't know is, the magical land has its own guardians. Guardians that won't let anything leave the land.
They are the ancient living beings of the land, developing and reforming the land to their likings. They hold three crystals, each with its own power that surpass the human abilities. They have been asleep for 1500 years, just to be awoken by human doings.
Some human doesn't like the ideas of exploiting the land as they fear they will be punished for their faults. Thus they join the magical creatures to fight for their own land. This is the least humans can do to redeem themselves.