Greatly reduces a target's Perception and Perception-based skills. Reduction depends on alter result over target control/Perception: 0-5 (-1 pip), 6-10 (-2 pips), 11-15 (-1D), 16-20 (-2D), 21+ (-3D). May affect multiple targets with +3 sense difficulty per additional target; highest target control/Perception roll is used for the group.