The Last Septarian

Matt and Kleo have spent their young lives training for an adventure, playing with swords and sparring against each other in hopes of one day needing these skills.
When Matt memorizes a map just before it is burned and lost forever, the two of them are dragged away on an adventure, not quite like anything they had ever expected, as the evil Enzo takes them against their will to an island far away.
Will they be able to escape him? And just what is it that he seeks in this remote place?
And what is a Septarian anyway?