Any spell or magical effect that causes the victim to become shaken, frightened, or panicked, or to suffer from some other fear-based effect defined in the description of the specific spell or item in question. In most cases, the character makes a Will saving throw to resist this effect.
Becoming Even More Fearful: Fear effects are cumulative. A shaken character who is made shaken again becomes frightened, and a shaken character who is made frightened becomes panicked instead. A frightened character who is made shaken or frightened becomes panicked instead.