A Perception Filter usually hides someone or something from the eyes of one or more people. Results can vary from an object or a person being rendered invisible to the viewer, be it an unwillingness to acknowledge it was there, or an extreme pain when trying to identify something under the effects of the filter. Perception Filters are frequently described by people who have come into contact with The Slender Man. They knew he was were there but didn't want to acknowledge that he was there, causing a conflict of interests in the viewers's own mind.
Sometimes servants of The Fears are capable of exploiting this power for their own usages whether it be by some manner of supernatural capabilities or technological such as the device owned by the Eden Organization.
- The term was coined in reference to the filter of the same name from British TV series Doctor Who, for its similar behavior and effects.