The creature can vaguely perceive you, using either a hindered Precise Sense (i.e. trying to see through a thick fog or foliage) or an Imprecise Sense. They can target you with abilities normally. When they use a non-Area effect against you, however, they must Succeed on a DC 5 Flat Check or the ability automatically Critically Misses and has no effect on you. They can use Area Effects against you without any hinderance.