The Silver Catacombs. Elfblood Trilogy, #2

Charlie has made his way to Kiloreen, ancestral home of the elves, in his quest to find the Silver Catacombs and the lost magic that lies hidden within. Instead, he finds a branch of the Elven Resistance Movement, a secret underground organization of elves bent on retaking Kiloreen and freeing their people. If they are willing to stand alongside humans, the elves will be a great help in the struggle against King Richard, but there is still the matter of the lost magic.
For if Charlie cannot find it, the war may be lost before ever it has begun.