Bearers of the Black Staff (Legends of Shannara #1)

Co-existing peacefully for five hundred years after creating their magically protected valley, the surviving members of four non-demon races band together against frightening creatures that are penetrating the shield around their home.

Sider Ament discovers unknown predators stalking the valley and realizes the magic that has protected the few survivors of humankind has faded, leaving them vulnerable to attack. Book #1