Dementation is the specialty Discipline of the Malkavian clan, and it has only one function: to share the mental illnesses and strange hallucinations that the Malkavians suffer from with everyone else around them. Depending on the Malkavian you ask, some will tell you that Dementation is a gift, a way to share the inexplicable insights and warnings that only they can see with other Kindred less fortunate; others will shrug and simply say that everyone deserves to experience what they do once in a while, or that they enjoy watching less mentally prepared people suddenly manage the bewildering effects they live with daily. Whatever the reason, Dementation has the effect of sharing a little bit of the Malkavians with everyone else - whether they want it or not.
Basic Powers
Passion: You may increase the emotions of one person in your vicinity three times over, fanning a small spark of discontent into seething resentment, annoyance into unreasonable rage or gentle fondness into passionate love. The person thus affected does not know why they suddenly feel so strongly, but they respond to it anyway, and do not know that any power was used to cause this shift in their emotions. You cannot choose what emotions to increase - whatever the person you target is currently feeling is immediately blown out of proportion, and more than one Malkavian has accidentally increased the intensity of an emotion that was definitely not beneficial to them. The newly heightened feelings last only for the remainder of the scene, after which the person affected returns to normal (although they still remember the feelings).
The Haunting: By subtly breaking down the image of normal, safe reality around them, you may afflict someone with the delusion that they are being haunted. They begin to hear strange voices and whispers that they cannot identify or find the source of, sometimes see what seems to be a shadow or a face out of the corner of their eye, become sure that something terrible lurks just behind them or out of sight, and suffer from the constant nervous breakdown of believing themself to be in continual supernatural danger. Mortals or Kindred who don't know anything about the occult are likely to believe that they are being haunted just like the protagonist in a horror movie; those who know a little bit about Wraiths or other frightening inhabitants of the astral realms might imagine that such beings have come after them. The haunting lasts for the entire evening and extends into terrible nightmares during the daylight hours; prolonged and repeated uses of this power on the same person may cause permanent traumatic damage.
Intermediate Powers
Eyes of Chaos: Things that seem like random coincidence or that "normal" Kindred would completely ignore have hidden meaning for you with this power, which allows you to see past the cracks and crevices of reality to recognize the underlying pattern that controls all things. You may gain insight into what is likely to happen for the rest of the current scene; you cannot be surprised, can accurately claim to have known things were going to happen, and may have a second to pre-empt various actions that you know are coming. Of course, it's not entirely accurate and you can't know all the details of events to come, and many Malkavians use this power simply to know, rather than trying to interfere with what they see as destiny unfolding.
Confusion: You may lay a shroud of confusion and muted unreality over everything that one person perceives, causing them to wander in a semi-daze, unable to recognize anyone they don't know very well or care about anything in the general wasteland of blank fog. They can still recognize normal landmarks and won't intentionally place themself in mortal harm, but they aren't capable of doing anything particularly important or difficult until the fog clears at the end of the night.
Voice of Madness: By whispering terrible things in someone's ear, you whip their emotions to unbearable heights, triggering a Frenzy immediately no matter where they are or what they're doing. You must be able to directly communicate with someone in order to use this power, and they will remember that you were present and acting to incite them later, although whether or not they know that you actually caused the Frenzy depends on how much they know about Dementation.
Advanced Powers
Total Insanity: By gaining your target's full attention for a moment, you may pull all their deepest traumas, fears, and mental anguishes to the forefront, inflicting immediate, debilitating stress and resulting mental conditions upon them. They immediately suffer from five random Derangements for the rest of the evening; the player must do their best to play the same character while dealing with the effects of these new and unexpected conditions, and will remember the experience on later evenings fully (although untangling it and understanding what happened may not be possible).
Elder Powers
Elder Malkavians have near-unlimited power over the mind, which they can use for good or ill as the whim takes them. Some of their powers include inflicting permanent Derangements on others, focused communication over vast distances with other Malkavians via the Madness Network, and even changing the innate permanent nature of any one of the Kindred who seems to deserve it.
Important Things to Keep in Mind
Derangements (and the real-life mental illnesses they model) are not convenient, funny, or easy to ignore; they cause very real and very difficult-to-manage effects, and any player affected by them should make the best-faith effort possible to portray them realistically. Users of Dementation may want to be sparing when it comes to affecting others; even a well-established court Malkavian might find themself bloodhunted if they meddle in the wrong person's emotions or show themself to be a loose cannon one time too many.