Fairy dust

One of the rarest and most highly sought-after substances, fairy dust is the most powerful hallucinogen known to exist. Made by fairies and sold by people crazy enough to bargain with them, called fairy brokers, it's highly exclusive and highly valuable for more than one reason. There are two main types of fairy dust: dream-laden and memory-laden. The former is used for recreational purposes, whereas the latter is an expensive commodity in the information business. When ingested, it sends the user on a powerful trip into the dream or memory that it's been infused with. The experience is completely immersive and involves all of the senses, not only witnessing but fully experiencing everything the original owner of the memory felt.
While one could barter with a fairy themselves, that job is best left to those rare souls inclined to go through this experience on a regular basis. Fairies are fickle things, and one must know what to value and when, for the price of a fairy's service is not anything materialistic, and rarely a favour - only if they are in the best of moods that day and want to let you off easy. No, usually a fairy will ask for whatever she finds funniest that you will give her at the time. This can be anything - the cherished memory of a loved one, the ability to tell left from right, the name of your yet incoceived firstborn child, the sensation of falling from a high place, etc. Over time, fairt brokers become increasingly peculiar individuals for this reason, and get that much easier to recognise and deal with. It takes somebody truly desperate to become one, yet cunning enough to do it for long and retire rich enough to enjoy what's left of their life as a barely functioning individual.
Because fairy dust is essentially enchanted with memories, witches are also able to produce a similar effect via liquid enchantments. They aren't as intense experiences, and the memory of them doesn't linger, but "liquid fairy dust" is a fairly cheap alternative. Of course unlike fairies, witches will never extract someone's memories, so they only make the dream-laden variety of the enchantment.

Properties

Material Characteristics

Fairy dust is the finest powder known to exist. While it behaves normally, easily scattered by air like sand or dust, to the touch it feels like a liquid such as water or milk. It is said that letting it sift through your hands is like gliding your fingers through the finest spidersilk.

Physical & Chemical Properties

Although the pollen is already enchanted with memories, it can be used as an ingredient in enchantments, and it behaves like expected, following all laws for preservation of properties. This does mean that the memory can be accessed by touching an enchanted object, however since the fairy dust is not consumed, the memory won't last and will fade away as soon as interaction with the object is ceased.

Origin & Source

Unsurprisingly, fairy dust comes from fairies. Whenever in the mood for it, a fairy can pollenate, releasing thousands of tiny specs. Nobody knows exactly which part of the fairy they come from, resulting in some even referring to the material as "arcane dandruff" in jest.

Life & Expiration

There has been no record of fairy dust expiring as far as anyone knows. Although most often procured with a purpose and used up almost immediately, there have been cases of people stumbling onto decade old vials, sometimes presumably even centuries old. By every account, time does not seem to affect it, whether in a container or not, sealed or not.

History & Usage

Everyday use

By far the most widespread usage of the dust is for recreational purposes. While each vial costs a fortune, that has never stopped the more fortunate to pursue unique experiences, sparing no expense. Neither its price nor its less than legal status have stopped wealthy aristocrats from indulging in trips of feverish visions. Anything goes, and depending on who can get it for you, it can even be tailored to your specific requests - whether you wish to daydream of flying on a dragon made of pastries or run around in a nightmare chased by dagger-wielding jesters with giant spiders where their face should be.
Of course applications and uses for fairy dust are as many as one can creatively envision, but among the more clandestine is the experience of other people's memories. In a world where knowledge is power, fairy brokers enjoy the benefaction of more than the wasteful your of aristocracy. From kings to assassins, any anyone in between, there are always those willing to pay the price of power.

Hazards

Continuous consumption of fairy dust is highly dangerous. It creates wondrous, fully immersive experiences, and most people who use it very quickly develop an addiction to the sensation. They crave it, more and more, always chasing the high of sensation like anything else. Those that indulge in the dream-laden dust too frequently soon become unable to tell dream from reality, even when they aren't on it at the moment. It's not unusual for them to become completely unhinged, and more than a few have lost their lives attempting the impossible before anyone could stop them.
But dust is dangerous even to those who take it less often, even if they are after memories and not dreams. To live with another's memory is a burden on the mind and can cause confusion, commulatively more so when the external memories are many, and from different people. It takes a strong and focused mind to not lose itself, or fracture completely, resulting in loss or split of identity.

Distribution

Trade & Market

Fairy brokers are the ones that specialise in the selling of the dust. They have the most dangerous part of the job - bargaining with fairies - and in return charge for it more than enough to deem themselves "compensated" for their troubles. It's hard to find them in smaller villages, but any bigger city is bound to have a fairy broker, often more than one. Because of the dust's legal considerations, they will rarely have a shop one can visit, instead using the criminal network to conduct their trade. Still, by nature of their craft they are most often quite peculiar individuals, and easily recognisible by anyone who knows what to look for.
Even a beginner fairy broker will usually start their prices in the hundreds of gold for a single via of dust, and that's not considering highly specific requests.
Witch parlors owned by the more brazen and idustrious will sometimes sport the "counterfeit"

Law & Regulation

Most places don't have specific laws regarding dust since it's extremely rare, however as an addictive substance it's automatically illegal everywhere such drugs are normally illegal. Emor, as the largest congregation of people, does have specific laws for its use, and strictly prohibits it outside three specific establishments and without strict observation. It also states that dust can't be used more than once per year per individual.
Notably, not only is the buying and usage of dust illegal, but so is the willing and knowing selling or coersion into selling of one's dreams. Many a fairy broker have been caught trying to persuade the less fortunate into selling their mental commodities for a small amount of money. Worse yet, they are often ignorantly happy to do it, not knowing just how much of themselves they lose in the process.

Type

Organic

Value

Ask your local fairy broker

Rarity

Extremely rare

Odor

While it's completely odourless to humans and the like, animals such as cats have been known to sense its smell. For some reason, dark elves can too.

Taste

It has no direct taste, and each portion tastes different. Instead, at all times, it has an aftertaste that you can never quite identify specifically, yet you know what it is. The right words for its taste are always just at the tip of your tongue.

Color

Fairy dust can come in all varieties of colour, though white is the most common one. Always interspersed are purple specks, the concentration of which depends on how dream-laden is the portion. Recreational dust is predominantly purple.