The Chronicles of Amyriad: Book 1: the Panacea

Peltrin has been training to fight since he was old enough to walk. By the time he reaches his mid-teens, he has proven his skills against full-grown, armed bandits. Everything changes, however, when he and his family confront assassins sent by the dark lord Aramir. Devastors-horrible magical creatures with deadly poison in their claws-terrify Peltrin to the point that he is unable to defend his family when they need him most.

Two are dead. Three are poisoned. Peltrin has only four days to find a cure. The path to the fabled panacea will require him to seek the help of friends both old and new. He must also come to terms with his crippling guilt and face the thing he fears.