The 15th Dragon — Frank Buchan

After the Battle of Castle Moor the land of Parthia lost its heroes, the Dragoneers falling just as did the Crimson Mages and the dragons they fought. Now, two decades later, a new threat has risen from the mountains. The young King of Parthia, faced with the reality of an impossible dragon under the command of an unexpected enemy, turns to the only man whose experience can perhaps turn the tide of a tragic war. But in a world where the enemy fights against slow genocide, and where the only hope seems to be a man broken by his past, long shadows are cast. And in this grievous time the fifteenth dragon becomes a weapon of despair, promising death to all.