The Fall of Heroes (A Narnia fanfic)

What if the well-known characters from C. S. Lewis's series, The Chronicles of Narnia, had children of their own who were someday destined to inherit the throwns? With a new threat rising, the royals place their trust and country in the hands of their children. How will these few teenagers save their land as well as the other fantasy realms in Fantasia?
All events happen before the end of The Lion, The Witch, And The Wardrobe before the Pevensies return home. Fantasia is all the fantasy realms (including, but not limited to, Neverland, Oz, and Asgard) united.