What is a Cleanser?
A Cleanser is an idea I had a couple years ago. A Cleanser is someone that has a very, very rare ability. Cleansing is pretty much burning off the psychic and/or magical aura on or around something and in essence purifying it. To do that you need a very specific mix of talents.
In comparison to the psychic to normal person ratio, the Cleanser to psychic ratio is actually a larger gap. It's not just being psychic or magically talented; it's being both in a very specific mix. It's - to put it bluntly - a "bit o' this, bit o' that" talent.
To start with one of the keystone abilities to make a Cleanser (pretty much one that the person has to have) is pyrokinesis. Not a lot, just enough to give them a spark so they can have a feel for starting fires, and controlling them. The other keystone talents are empathy, aura seeing or feeling of a decent strength, telemetry (which is getting a feel and sometimes visions from touching objects), and magical ability with a strong fire affinity. Other psychic talents are nice to have for a Cleanser but not a must. Nice - helpful even - but not really necessary.
Anyway when you get the proper mix of abilities you get someone who will be able to make psychic fire. And unlike physical fire, water won't quench it because the fire's not on the physical plane, but rather on the spiritual or astral plane. It will only burn so long as it has fuel, so as long as the object burning has a mystical or psychic aura it will burn. Leaving the object clean or any aura, taint, or energy; in essence purified.
Now like any pyrokinetic of decent ability the Cleanser can control or put out the fire at will - with practice. Cleansers are pretty much always the result of the mixing of bloodlines. Pretty much one line having magical talent and another psychic and mix them and you have a likelihood of somewhere down the line of a Cleanser being born if you're lucky. However it has to be the right talent and ability mixing to make a Cleanser - thus them being obscenely rare.
Now here's where things get kinda complicated: Cleansers being what they are, are not only extremely dangerous to supernatural creatures, they're also highly prized. To get a Cleanser on your side is an extreme boon, however to make one an enemy is something to be feared. Demons and other supernatural creatures that are made up completely or mostly of mystical or psychic energy greatly fear and covet them.
Mostly because they're not only dangerous to them, but the very fact being what their ability is makes them deadly to most supernatural creatures. And something that is not used to feeling fear towards humans will always try to destroy that fear if they can't have it.
And Cleansers don't even have to just kill or destroy what they're purifying. Cleansers with enough control and power can do a lot more. Cut the ties of contracts, burn off demonic (or angelic for that matter) taint, most everything a demon does - or works on a - Cleansers can destroy by burning it with their psychic fire and leaving nothing but the psychic equivalent to ash behind.
Curses and blessings alike can work on a Cleanser so long as they never use the fire on themselves, however if they do they can remove just about anything from themselves except their own ability because they themselves are the core of the fire, so nothing will burn hotter or purer for them.
This also leads to the death gift of a Cleanser. This is when a Cleanser gives up their life taking out something that they would normally not be able to do, using their entire being to purify it.
Now for the Cleanser Arc I'm writing:
Dean is a Cleanser; and a strong one at that. Now Dean among the talents he has that make up his ability has just enough precognition to be able to have subconsciously known that if he got found out by what they're hunting that he will be in very deep shit. So Dean found ways to hide and burn off the energy. His pyromania, putting enough energy in the fires from whatever he's burning at the time to make it work a bit better, and also using Sam to camouflage himself.
And it worked very well. However when he got put into a situation where not only he himself, but his brother and dad would have been killed by demons with no physical bodies he lashed out the only way he could and hurt them. This drained him a great deal more than he was used to, having before then only having used tiny sips of his power, so his body went into shock, but it did however take care of the problem, and once the fire started it would burn until it ran out of fuel (the demons were dead) or it got put out (with the magical equivalent of water, pretty much something that nullifies psychic and magical ability)
Now because he's outed himself and he's a hunter that does it for the right reason (to help people) he has made his way onto the demon's ten most wanted list. They might try once, maybe twice to get him to join them, but after that they'll being trying their damndest to off him. Because Cleansers are not stuck with just expelling a demon from a vessel and sending it back to hell, no they can actually kill them. A walking, thinking, and reasoning weapon.
Also I would like to note that Dean's actual normal pyrokinetic ability is about enough to light a candle with a lot of effort and an extreme headache afterwards. He's actually heaver on the empathy and magical talent end of things. As well as having, as I mentioned, very slight precognition, he gets the equivalent of subconscious hunches with the talent. Though he does get normal hunches, they almost never have anything to do with precognition and more to do with good instincts.