A Dragon's Lament — River Fairchild

Book 2 of the series.
Magic is real. So is betrayal.
David enters the Fire Kingdom and events shift from bad to worse. He learns a shocking truth about the dragons, a truth destined to block his efforts to retrieve the lost magic of Shaylar from the ruling Council. After a cave-in and injuries force a rescue, David finds himself more isolated than before as personal concerns scatter his trusted advisers and the wizard who led him there abandons him.
The head of the dragon Council negotiates separate deals with both David and his father, sowing further discord between them. David's close friend, Lothan, disappears into the caves and doesn't return. A group of dissidents kidnap Wilks, the child empath David is sworn to protect. With no options left, he accepts the Council's demands to help them in their centuries-old conflict, risking a war which might kill them all.
Even if David manages to win, there's no guarantee the dragons will let him leave the region alive. They don't want the Kingdom of Shaylar to rise again and will stop at nothing to see it remain a pile of dust.