The Magic Medallions — Tim Murari

A massive undersea earthquake frees the evil kingdom of Gondwana. Its empress, Cremelle, is ready to lead her partly human inhabitants, trapped below for millions of years, to conquer earth. All that stands in her way are Axxiss, an American, and five other teenagers from different countries of the world who have one thing in common - a medallion that was mysteriously put around their necks, and that cannot be removed. What is the medallion? Why have they been chosen? Who sent the dog which appeared out of thin air and says they have to find the key that will lock down Gondwana forever? Will he be able to save the children and guide them through the complex maze of history, space and time to find the key?