Fear play describes any sexual activity that involves the use of fear to bring about sexual arousal.
In fear play, an individual's terrified mental state triggers a rush of adreline which causes arousal. Fear play is different from masochism, in which arousal is caused by an endorphin rush.
Fear play falls into a category of BDSM-related activities, marked by high physical or psychological risk, called "edge play."
Some forms of fear play may take advantage of a person's pre-existing emotional doubts and fears, of abandonment or humiliation for example, while others work on a physical level. Physical forms of fear play include medical play, knife play, and kidnapping.
This is a basic roleplaying scenario. You're the rapacious pirate plundering the village; she's the innocent maiden in the local town. (It works particularly well if you have an eyepatch and a bandana.) She's at home alone, minding her own business, when you come crashing through the door. She struggles, of course, but she's helpless to resist you. Swooping down on her, you bodily rip her clothing from her and pin her against the wall. You hold her there by the wrists while you explain what you're going to do to her. Then, finally, you ravish her until you're thoroughly satisfied.
Harpaxophilia is erotic arousal from the thought of or act of being burglarized or robbed. It is similar to chrematistophilia.
In a real to life, this can be quite dangerous. Some may choose to safely role play the fantasy version of being burglarized. Robbery play can be the focus of a scene or part of a larger scenario like a play rape, hostage, or kidnapping scene.
Knife play is a BDSM activity that involves blades (knives, swords, or daggers, for example) as a way to produce fear and excitement in a submissive partner. The blade is usually used to cut away clothes, may involve sensation play (scratching the skin) or temperature play (making the blade hot or cold).
Knife play can provoke a pleasurable sensation of fear in submissives. As with all BDSM play, as long as knife play is safe, sane, and consensual, it can be a great way to explore to safely explore fantasies of being dominated.
However, knife play can be dangerous if not handled carefully. A sharp blade can cause deep cuts, leading to major blood loss. As a result, this activity should be done only with the utmost attention, care and knowledge of the submissive. One way to simulate blood (especially for a blindfolded submissive) is to hold the blade under warm water and then run it, dull side down, on the skin. The water will feel like blood.