Spells (3e)

Only the spell’s subject can see the phantasmal killer. The character see only a shadowy shape. The subject first gets a Will save to recognize the image as unreal. If the subject fails, the phantasm touches him, and he must succeed at a Fortitude save or die from fear. Even if the Fortitude save is successful, the subject takes 3d6 points of damage.

If the subject of a phantasmal killer attack succeeds in disbelieving and he is wearing a helm of telepathy, the beast can be turned upon the character. The character must then disbelieve it or suffer its deadly fear attack.