Do you know some evil? You don't even have to be evil. Just know of some. Or seen it. Or heard about it. Read about it in a magazine.
You will burn.
Ghillie suits are suits of mossy foilage armor that grant limited powers to their wearers and fall apart once it rains. The benefits are obvious, but will be stated here nonetheless because that is what a fucking wiki is for:
1. Tricking bigfoot into wanting to have sex with you. This is by far the most common requirement, as way more humans than you may expect desire to catch and fuck bigfoot, and thus gets it first place on this list.
2. Swamp navigation. The ghillie suit makes you a better tracker and survivalist in heavily forested and swampy regions, whether you are in that region or not, whether you need to or not, and whether you like it or not. It works especially well since the ghillie suit actually attracts additional moss and foilage as you wear it. This can become a problem, for obvious reasons that will be spelled out in #5.
3. Burning touch. The ghillie suit allows you to, upon mere touch, immolate any and all other humans who have at any point ever recognized the concept of evil. This does not work on children, but there are mods for that. The reason this power works is probably biochemical, or due to some odd infection (see #5 below). The only drawback to this power is that you will not be informed by the suit beforehand who is and isn't aware of evil, and you may end up killing your best friend trying to high-five him after burning some unwitting philosophy students. These do not effect the wearer.
4. Camouflage. Some people use ghillie suits to blend into their surroundings, which is admittedly much more effective in the woods than on a city bus, which is why this skill is ranked so low. They are valued, however, in preventing you from being picked up by Predator's thermal vision.
5. Moss collection. An even smaller group of people collect moss, and just want the moss. They wear the ghillie suit until it covers them in moss, then they have that moss. They must be careful not to become subsumed by the moss, lest the moss become them and they become the moss. You surrender thought and voice and identity to the moss. All is moss. All burns by moss the unburning, for which their is no cure but only relief. Nobody wants that.
Ghillie suits are often used by hunters to blend in, navigate, and burn any adversaries all in their quest to fuck bigfoot. Others let the mossy power go to their head, until they become unthinking mute swamp beings with little to no human semblance left. Others claim that their ghillie suits started moving on their own, without being worn, and would stalk the grounds around their cabin looking for odd jobs to do and rusty old equipment to cover in moss. But ninety-nine times out of a hundred, if you see a ghillie suit walking around or even just standing still staring at your front door for days on end, there's probably a dude in it. A dude that wants to wank all over Bigfoot's chest and then take a blurry photo of it.
Ghillie suits are created by βρύοmancers who toil to bind the suits in a golem-like state of neither life nor death, but servitude to their eventual owner with dark secret seals that can, like most magic, get far out of hand and backfire on their Master. This makes authentic ones (not reproductions or knock-offs) very expensive, even though all types will just fall apart the first time they are rained on by any non-swamp water.
As armor they are pretty useless because arrows, let alone bullets, tear the thing to shreds with any meat entity inside. Ironically, they can also be killed by conventional fire, even though they are immune to magical fire spells. So just kill it with regular fire, I guess.
Another terrible side-effect is that anything you consume or drink while in the ghillie suit will taste like swamp. This has nothing to do with the βρύοmancy involved, just the practical fact that you are straining your sustenance through a filter of pure swamp material.