Well maybe you could have the enemy of the faries attack the group of friends at the pond. Maybe kidnap one and then that friend ends up to have fairy blood line or something. And either begins turning into a fairy or is a rich blood heir next in line for the fairy throne.
Then they learn the magical world is dying and unless the friends get the 3(/how ever number you want) magically stones(/other item) all magical creatures will die and so will their friend.
Or i dont know. Think its good or something else you might have in mind?