The High King's Tomb By: Kristen Britain (Green Rider Series #3)

More than a thousand years ago the armies of the Arcosian Empire, led by Mornhavon the Black, crossed the great sea and tried to conquer the land of Sacoridia using terrible dark magic. Eventually Mornhavon had been captured, and his evil spirit imprisoned in Blackveil Forest.

Since that day, the perimeter of Blackveil—now a dark and twisted land—had been protected by the magical D’Yer Wall. But in the centuries since the war’s end, knowledge of the working of magic had disappeared from Sacoridia, due to the fear and prejudice of a people traumatized by Mornhavon’s sorceries.

Karigan G’ladheon was now a seasoned Green Rider—a member of the magical messenger corps of the king. But during her first year as a Rider, a rogue magician had cracked the mighty D’Yer Wall. The spirit of Mornhavon, sensing the weakness, had begun to wake, seeking vengeance, and causing frightening aberrations throughout the land.

Karigan had managed to transport the spirit of Mornhavon into the future, buying valuable time for her king and country. But how far in the future was Mornhavon now? A hundred years? Ten years? Only one year? There was no way to tell.

And though Karigan and her fellow Riders scoured the land searching for lost magical knowledge, and members of Clan D’Yer camped at the wall hoping to uncover its lost secrets, they were unaware of a threat to their kingdom that lay far closer.

For there were Arcosian soldiers who’d survived the Long War, and the descendants of those ancient enemies had spent generations honing their powers of dark magic—a force against which the Sacoridians had no defense….

Goodreads: 4.25

Hardcover, 2007