With Idolum the illusionist creates doubt through passing false images across the surface of the target’s thoughts. By focusing his attention on the target for 1 round the illusionist creates images, related to something the target is talking about or doing, that makes the target question their own actions. The target is allowed a saving throw. A successful intelligence check lessons the impact of the spell, so that the action, whether combat oriented suffers a -2 penalty. If the target fails the intelligence check, they do not carry through with the action.
The illusionist must have some idea about what the target is doing. The do not have to speak the language.
For instance, the illusionist sees an ogre preparing to attack him. He knows the creature’s intent and inserts an image of the ogre being struck by lightening when he approaches the illusionist. The ogre is taken with fear and either calls of the attack and flees or suffers the necessary penalties