The Oracle's Prophecy - The Oracle, #5

In ancient times, five dragons fought against an immense and powerful evil. Unable to defeat Sin, they imprisoned it in ice. The Oracle vowed to watch over the land and protect it from further threat. Her brother, the Sentinel, promised to oversee the ice prison and ensure the creature never escaped. Thousands of years have passed since that time, and still the Sentinel sits in his lonely Tower, watching and waiting. A simple farmhand, Corey doesn't know what to make of the way his aunt and uncle abruptly drag him into a journey across the frozen tundra, or why he's had to abandon his life to live in the Tower complex.
The only consolation from his new, strange, and confusing life is the mysterious man who lives alone in the highest room of the Tower. When his help is needed to defeat the forces of evil, Corey steps up to assist the Sentinel in banishing Sin for good.