The Ruin of Staspin - Argetallam Saga, #6

An assassination ends negotiations in Brevia before they've begun. Janir and Saoven hurry back to Adasha to find their city under siege by Prince Malkalar's elven armies and their former allies. With their defenses weakening and no hope of reinforcements, their only hope is a rumored power in Janir's bloodline. Only she can awaken it, but if she fails, it will mean the extinction of the Argetallams and a genocide like the world has never seen.