Game idea - Creating potions and other consumables

First, a quick word on potions and other consumables: unless the adventure's progression hinges on a potion's effect(s), I like to let the players examine potions at their will and not blatantly explain them. Personally, I also tend to stay away from magical effects in potions, preferring to leave magic to strange items and the people who cast them. Maybe it's just my experience, but I've found that using magic items with fantastic effects often leads to excessive metagame commentary. (For example, I introduced a potion of demonic possession in one game; it lead to a half-hour conversation on whether demons could inhabit bottles.)

When creating potions, use your senses to make them lively. Here are a few good questions to consider:

• What does the container look like? How big is it?
• What material does the container comprise? (e.g. Glass? Wood? Metal? A corked skull?)
• Is the container's material colored or opaque? Old or new? Brittle or malleable? Etc.
• What material does the container hold? (e.g. Liquid? Powder? Gas?)
• What color combination is the held material? Any other descriptive words come to mind?
• What consistency is the material?
• What does it sound like when the potion is disturbed and scrutinized?
• What's its full name? Is it scientific? Arcane? Folky?
• And of course: what are the effects? How long do they last? Could they break the game?

For your own purposes, you should keep track of the metagame details:

• How can you connect this item to the plot?
• Anticipate what your players might do with it: might they apply it to a weapon? Mix it in a drink?
• Who might be immune to it? Is there an antidote that might help you move the plot?
• Where is it found? On an apothecarist's shelf? In a suspicious satchel? Hidden in a tree trunk?
• Why is it found in this particular location? For roleplaying reasons? To flesh out a location? Just for fun?

Lastly, here are three examples of potions. The first is factual, the second is a mix of details and story, and the third is just story:

Effusion of Dropknife - On a small shelf next to an assassin's weapon rack rests a dusty, brown glass bottle. Beside it lies a pile of some rusted blowdarts, arrow-tips, and a dull razor. It looks like the bottle hasn't been disturbed for years, but the infamous, hand-scrawled name on the label is still legible: Dropknife. When a few drops are added to a drink, this paralyzant, a respected addition to any rogue's occupational inventory, causes the drinker's hands and feet to tingle and go numb for up to a half-hour, rendering useless one's abilities to pick up objects, manipulate weapons, and ambulate normally. Although it is tasteless, odorless, and clear, those familiar with it will warn potential users of its tendency to thicken any solution it's poured into. Dropknife's ubiquity is due to its common effect on most humanoids. Only a few drops are needed; anyone who has ingested more has either asphyxiated due to muscle inactivity or fallen victim to a more violent death.

Fleshwood extract - My side was killing me. Walking 10 leagues with a host of old war wounds will do that to an old man. I began to feel as derelict as this run-down border town we arrived at three days ago. I've been sitting up in bed at the local inn, unable to walk, but this morning a maid saw me in my pathetic state and pointed me to a shoulder bag someone forgot after leaving the inn last week. It was mostly empty, but I noticed a familiar, small, corked ceramic bottle that was laquered with an off-white enamel. A somewhat-useful folk remedy, extract of the fleshwood tree primarily causes the drinker's skin to look grainy and knotted for a day or so. It's a rather unattractive state, if you ask me, but the wonderful side effect is that this process heals scar tissue and other chronic skin and muscle injuries for a time. War veterans like myself will sometimes talk of "going grainy" to help with chronic pain. If you can put up with the bitter, piney taste of fleshwood--I like to mix mine into beer, nature's other wound-healer--this'll give you a couple days of pain-free walking.

A large glass jar of swirling blue oil  - I know two things about this jar. First, old Barl Eggthorn's idiot son Danney drank this on a dare and we all watched him turn white and walk right into the ocean. We would have stopped him except for those swirling tendrils of icy smoke that came out of him. Nobody wanted to get near those things. Hell, I tried to talk some sense into him, but the closer he got, I started to hear screams. Some of them were my own, to my surprise, but some came from the direction of the beach. It took a while to get up after he walked past me and the other folk. The second thing about this is that no one knows what to do with the jar. Anyone who picks it up instantly loses the desire to get rid of it. It's not that they want to keep it, it's just that they feel like they just can't part with it. Even throwing it into a bag and carrying it out that way has this effect. So as you can see, we're stumped. No one can even say for sure how it got onto that basement shelf. But for now, we've chained and locked the door, and there's not one person in town who even wants to broach the topic of this particular depravity.