I Know What You Fear

Basically the power to discover other people's fears. Often necessary for a "What Do They Fear?" Episode. This power can come in several forms: Type 1, Type 2 and Type 3

Type 1 is the power to know what a person's fears are. For example, one could see a picture in your head or somesuch similar thing. One then has different options to use this info. This type does not necessarily include the ability to project those fears into people's heads and they may have to be exploited in a more normal way, such as dropping them in a snake pit or a sewer full of rats.

Type 2 is the power to bring a person's fears to life without actually having any knowledge about what those fears are, this power does not deliberately cause a person to believe they are, for example, vomiting worms, it's just the effect of the power on that particular person. It is sort of like infecting people with dread.

Type 3 is the power to see a person's fear and/or show them their fears (if they have several). Control is near-absolute and often includes intensity and duration. A character with a Type Three power will usually have some kind of psychic or illusionary power to bring the fears to life.

It goes without saying that this is usually a bad guy power.

Comic Books

 * Dani Moonstar in New Mutants created illusions based on the target's worst fears, as did Teen Titans villain Phobia.
 * A variation of Type 2 appeared in Brian Michael Bendis 's Alias. In Volume Four, Jessica comes face-to-face with occasional Daredevil villain (and Jessica's archenemy) The Purple Man, whose body secretes chemical pheromones which, when inhaled or absorbed through the skin, allow him to control their actions by verbal suggestions. (The Purple Man, like The Joker, is aware that he exists in a comic book). He orders Jessica to imagine the most horrifying thing she can envision, which turns out to be the corpse of her boyfriend (Antman II) covered in ants lying in her bed. The Purple Man comments that he wonders what she is seeing, guesses "it doesn't work that way."
 * In Batman, "The Scarecrow" has the power to discover and induce a person's greatest fear. (Ironically, poetic justice proves his own greatest fear turns out to be-- a fear of BATS!)
 * This seems to be a major theme in The Dark Knight Saga, especially in the first part, Batman Begins.
 * Trauma of Avengers: Initiative actually transforms into what his target fears, giving him whatever physical attributes and/or powers that go along with the new form. This combination of psychic powers and shapeshifting was considered a "holy grail" of mutant powers by Gyrich.
 * It should be noted that this is imperfect--he went through four forms trying to find a weakness in The Incredible Hulk (who, as it turns out, isn't afraid of anything), and got tossed into a parked car for his troubles.
 * Gen 13 villain Phobia was a creepy little girl with Type 3 powers.
 * The Sinestro Corps of the Green Lantern comincs is based entirely on this concept. With their power rings they can create constructs of both their own fears and their victims.

Film
"Tangina: Now clear your minds. It knows what scares you. It has from the very beginning. Don't give it any help. It knows too much already."
 * Poltergeist. According to their psychic medium consultant, the ghost causing the Freelings all the trouble has this ability.


 * Among Shang Tsung's powers in Mortal Kombat is the ability to see into a person's soul and find out what that person fears most so he can use that fear against them, making this a Type 3 power.

Literature

 * Boggarts in the Potterverse take the form of a person's greatest fear, which means they have this power.
 * As do the phobophages in The Dresden Files. Since their intended victim is at a horror movie convention, this results in Captain Ersatzen and Shout Outs aplenty.
 * In the Belgariad's prequels, Polgara's Mind Rape persuasion method is revealed to be this. It only failed once, because the target was on drugs (note that if she put much effort into it, she probably could have un-drugged him like Belgarath did in the prequel).
 * Type 3 in Nineteen Eighty-Four, through sadistic government research on individuals and a "Ministry of Love" dedicated to custom torture.
 * The Wardstone Chronicles includes a secondary character with the ability to do something called the Dread, which is a Type Two power.
 * The Books Of Bayern include several characters, mostly antagonists, who are capable of knowing exactly what one fears (mainly things like public humiliation or loss of control, which are the things behind fears like acrophobia or arachnophobia) and also what a person wants, desires, or intends. Their power also gives them the ability to know precisely what to say in order to get what they want. Yeah. It's really no wonder they're mostly Bad Guys.
 * The third book of Midnighters has a peculiar scene where, the group's Half-Human Hybrid, attempts to intimidate a minor character. He somehow knows (without knowing how he knows) that said character is afraid of snakes, and his appearance and posture shift in just such a manner as to bring up thoughts of snakes, without changing blatantly enough to be obvious Shapeshifting.
 * Amanda Reese of the Fingerprints series was a Type 1.
 * Elva from the Inheritance Cycle is a heroic (well, kind of) example. She has the ability to sense a person's negative emotions, including fear.
 * The Furies in the Star Trek quadrilogy of the same name have this as their main weapon: a directed-energy beam that forces anyone who is hit by it to experience sheer terror.

Live Action TV

 * Barbas, the Demon of Fear in Charmed, is a Type 1. Played by Billy Drago (John Bly from The Adventures of Brisco County Jr).
 * He made several appearances throughout the duration of the show, becoming important enough to have a Good Counterpart shown in the Mirror Universe episode. The sheer contrast between the personalities and actions of the two is rather hilarious.
 * Star Trek the Original Series episode "And The Children Shall Lead". Gorgon the Friendly Angel taught the children the power of learning another person's fears and using the fears to disable and control them. The kids caused Sulu to see swords surrounding the Enterprise so he wouldn't change course and used Uhura's fear of dying to prevent her from calling Starfleet Command.
 * The alien monster in the Doctor Who story The Mind of Evil attacked people with hallucinations of their worst fear.
 * Similarly, the hotel in the God Complex.

Tabletop Games

 * The Dungeons and Dragons arcane spells Phantasmal Killer and Weird are Type 2, as they do not require knowledge of their victim's worst fear in order for them to work.
 * Warriors of Heaven has a nonlethal version of the first, 'Phantasmal Terror'. 'A Guide to the Ethereal Plane' introduces the unfortunate result of 'Phantasmal Killer' turning real, as illusions sometimes do there -- Fær, the monster who polymorphs into the victim's nightmare and kills by touch, but isn't resisted as easily as the original spell (it is for real this time).
 * The Dream Larva is the manifestation of a god's nightmare, with the ability to shape itself into anyone's greatest fear.
 * In Changeling: The Lost the first "clause" (read: skill) of the fleeting autumn contract allows a changeling to do this.
 * In In Nomine, Calabim that serve the Demon Princess of Nightmares can see a person's worst fear.

Web Comics

 * The Head Alien has a list of his enemies' fears and tries using it on Joe. However, since he mostly focuses on Joyce and Walky, his list isn't really accurate.

Web Original

 * SCP-825 is a helmet that has this effect on its wearers, presenting them with increasingly horrific visions based on their worst fears.

Western Animation

 * The Fear creature from Extreme Ghostbusters.
 * In Lilo and Stitch, Experiment #300 has the ability to determine and mimic a person's greatest fear.
 * Professor Screw-Eye from We're Back!, has invented a radio that allows him to know what scares people.
 * The Shadow of Fear from Xiaolin Showdown is a rare form of both Type 1 and 2. In order to know what a person fears, one has to use it's first power to literally enter someone else's mind; the person using the Shadow of Fear also has some serious reality warping abilities in this state. Once a person has delved into victim's mind long enough to know what they fear, a person can then later use that knowledge to bring their fears to life in the real world.

Video Games

 * Some of the ghosts from Ghost Master have the power to discover peoples unconscious or conscious fears. Often it's up to other ghosts to exploit those fears.
 * In The Legend of Spyro: Eternal Night, the final test to meet the Chronicler is to face the thing you fear the most. It's not explained exactly which Type it is, but it takes the one taking the trial's worst fear and makes an energy based version of that fear. In Spyro's case,
 * Cynder gets a Type 2 with her Fear element in Dawn of the Dragon. It allows her to paralyze opponents with fear, either by letting out a sonic scream or blasting them with red energy spheres. Either way, the fear infecting is a secondary effect along side damage.
 * Darth Phobos from Star Wars: The Force Unleashed can use The Force to probe someone's mind to find their fears and create illusions of it. In her boss battle, she puts on a Shapeshifter Guilt Trip, as Starkiller's greatest fear is Juno Eclipse's death.
 * Tatari from Melty Blood is a vampire that is repeatedly created from rumors, and has the ability to manifest people's subconscious fears as reality.
 * Wizeman from Ni GHTS Into Dreams, being the god and creator of nightmare, is implied to have this power. He can also alter the dreams of visitors or create nightmarens in order to take advantage of these fears. He even uses it in the second game to steal Helen's red ideya by removing all light from her dream (Helen is deathly afraid of the dark).