In order to power his experiments, Orac used powerful potions brewed from the spores of these deadly mushrooms called Night Caps. When simply eaten, the night cap is but a poisonous mushroom, it is only when its power is extracted by an alchemist or fae does it become truly special. It looks like a tricholoma argyraceum, though with hard to see black veins running amongst the others on the underside of the cap. These fungi grow almost everywhere, but always seem to grow closer to places where people have felt despair for a long time.
The link to despair tends to lead foragers and witches to give them a wide berth, since the magic in them does not seem to be safe. When they are used in spells and medicine bags, they tend to be part of a formulation to bring despair, but it always works in the form of bad dreams. When eaten, those dying of their poison report feelings of fear and horror and eventually midwives and barbers find their heart stops, seemingly due to the agony of it all. Because, Night Caps are not properly mushrooms. They are a minor fae plant which is fertilized by despair. Most sages who specialize in plants are aware of this simple fact.
While most plants are properly of this world - sometimes things from outside slip into the world. Creatures of dreams and oaths like the fae are very important to humanity, and the goodly folk are often the only thing keeping peasants going from day to day, keeping their hopes and dreams alive. The other side of that coin is what feeds upon the peasants as they endure the hardships of the nobility and their harsh taxes and abuses. People fear the strange queens, the dullahan, or the headless wisps which live in the moors, but more minor things grow, and night caps are one of the most benign of the things that could fester in a wasteland of hopelessness.
During his experiments, Orac started by dissecting several Sidhe Folk in order to try to understand the nature of dreams. The problem of course is that they did not seem to properly contain organs or other insides. The first he tried was simply stuffed with straw, the second contained only moonlight, and his final attempt found the entire body to be filled with living butterflies. These experiments also caused him to spend the rest of his life hunted by fae, and indeed, were the reason he was finally brought low. The fae stitched him into his own dreams, leaving him lost in his own Dreamworld forever.
Orac's next experiment involved several fae plants, finally settling on the night cap. He used alchemy to bring out the essence of the thing, bringing forth emotion and hopelessness, and then began to slowly drip this essence onto the forehead of sleeping victims. Since he experimented on captives, the Night Caps reacted very strongly to their dreams. The essence of the night cap began to collect the dream itself, and took on a translucent smoky hue, looking almost like bottled darkness. These dark dreams could then be drunk to experience the dream, or, if the sleeper was placed within a Prison Circle (see Summoning in the Burning Wheel Codex), released as a Free Belief on its own, often expressing the person's desperation or their final hopes.
Night Caps can also be used as part of a Folk Ritual which involves despair or hopelessness, though some have managed to use the spores of the Night Cap to suck despair from someone, warding off a Black Dog or curing the harm of a Spectral Echo. They can also be used to make a very deadly poison. Having access to Night Caps gives +1D to Vile Poisoner or Poisons skill tests to manufacture poison. Any use in ritual magic, alchemy, or even the poisons skills requires the user to make an Ob4 Agility or Perception test to not make a mistake and inhale or ingest some of the poison (though this minor mistake gives a +1D Health to resist the affect due to the small amount).
If a Night Cap is ingested or the spores inhaled, the poor sod immediately gets a +1Ob penalty to all Skill and Stat tests due to growing despair. This penalty increased by +1Ob per day until it's at it's worst of +5Ob. Each day the imbiber can make an Ob5 Health test to not increase the penalty. After Will hours, the victim also receives a Traumatic wound, as the despair begins to crush their body, their blood flow begins to slow and their heart begins to give out. This wound deteriorates like a normal wound, only deteriorating maximum once (which is more than enough to kill most creatures). Quickly getting a very skilled doctor is the only way anyone has ever recovered from Night Cap poison.
Recognizing Night Caps, and especially telling them from other edible mushrooms is an Ob3 Foraging test, or similar skill for knowing the safety of mushrooms. While they are wild and deadly, they are fairly easy to tell. Recognizing them when they are cut up or cooked is another matter, and that is up to the skill of the poisoner. The poisoner is advised to discard the cooking vessels and knives they used, since even trace spores can be incredibly deadly.
A Burning Wheel Monster Every Week