The Grove of Sacrifice — Meg Hendry

Rien knows who he is, but that might not be enough to save him. The Sancta is seeking a lost relic of the All-Keeper that they hope will help them destroy wild magic and all who use it. There's far more to this weapon than the Sancta knows. The All-Keeper himself knows the truth, but the Sancta are too far gone to listen, to believe it's him if he appears to be against their plans. It's up to Rien and his allies to stop the Sancta, and to stop the gods from being the end of Ivrua. The Grove of Sacrifice is a novella.