TerradonBook - 2011
Five boys must guard the border-wall on Earth that separates humans from the mega-beasts. Battles won by the border guards earn them upgrades in their battle gear. Battles won by the mega-beasts give them more power. In this book, Kai faces the beast from the rock world.
Publisher: Toronto : Scholastic Canada, 2011, c2010.
Characteristics: 76 p. :,ill. ;,20 cm. --