The Blue Goblin Pill
In the darkest, coldest caves grows a very rare, small mushroom: the Blue Goblin. It grows in patches a couple feet wide; under direct sunlight it melts in less then one hour, leaving only a stinking blue puddle.
If eaten, it causes nausea, headache and fainting fits, as most mushroom experts know. Some beasts, though, seem to be immune to its effect and actually feed on the patches they find. As some alchemists know, the mushroom is also one of the ingredients for the infernal love potion .
Yet, lost among the lore of the shamans of the wild men of the mountains is the secret of this mushroom: if dried properly, slowly and in the dark, it leaves a fine blue dust, which has none of the ill effects of the original mushroom.
Argaiv Silaic, a wise, excentrical explorer and physician, once discovered its secret, and had a chance to note what he found out before becoming a sacrificial victim to the Dark Goddess of the Mountain. This is what he scrawled while locked inside a wooden cage:
The dust from the blue goblin, mixed with mountain goat butter, is shaped into very small blue pills, which the shamans call 'the bluenuts'. Eating one of such 'nuts', seems to increase 'rod' size, hardness and duration, and improves the quality of the whole 'interaction'. In order to comprehend more, I really should try one, if I ever get out of this cage.
Years passed since that unhappy incident, which culminated with poor Argaiv hurled down a slope, and the secret remained confined among the wild men and their wild midsummer celebrations.
One day, though, a "lucky" man came back to town with the secret! He had been the wild tribes' prisoner for a few weeks, and, exactly like the wise Argaiv, he got to know everything. But he managed to escape. Artivel -this was his name- came back to the Capital City of the kingdom, eager to share the secret with his associates in crime and enlarge his bussiness, expanding the offer of forbidden substances for those who enjoy the night life.
Even though the mushroom is rare and the pills' preparation takes some time, the goblin's pills are quite known in larger cities of the kingdom and, despite low availability and high price, people smile and whisper of nights and parties gone "into goblin"...
-Enough is enough. The city seems to have undergone a wild change: during the day, most of the population looks tired and dizzy: workers, artisans, even guards keep yawning... During the night, the streets are strangely full of lights and people, houses of ill repute literally burst with merry, eager customers. People from the outskirts and close villages swarm into town and seem very unwilling to leave, even though they don't seem to have a proper job.
The local Church of Good Behave wants the PCs to investigate!
A smart alchemist, in league with a band of yellow lotus dealers, has found a way to grow more and more mushrooms in easier facilities, and thus has flood the city with millions of blue goblin pills.
Will the heroes uncover the secret? Will they decide to stop it, or fall prey to the thousand temptations this investigation holds for them? Will they manage to bring normality back to the city before the barbarian hordes' assault?