Bearers of the black staff / Brooks, Terry

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

Sider Ament discovers unknown predators stalking the valley and realizes that the magic that has protected the few survivors of humankind has faded, leaving them vulnerable to attack and forcing Ament, two young Trackers, and an elf princess to risk their lives to warn others of the danger.