Glowcap Mushrooms (3.5e Equipment)
From D&D Wiki
A form of mushroom found growing underground in dungeons often, it glows with a pale blue light due to the bio-luminescent chemicals contained inside. It has a very light 'tangy' flavor like extremely dilute lemons. They make fine rations for dungeon dwelling heroes on the go, and provide light akin to a candle (in large batches they can provide light akin to a torch).
With a Craft (alchemy) check of DC 20, you can prepare them as optional spell components. As spell components they may be added to any electric spell to increase the damage done by +1 per level of the spell. So a Lightning Bolt (3rd level spell) deals it's normal damage +3. For each level of the spell you need an additional dose of Glowcap Mushrooms, so the same Lightning Bolt takes 3 doses of Glowcap Mushrooms.
If plucked from their source they last for 2d4 days before becoming dry, flaky, and inedible. This reduces to 2 days if exposed to a bright or dry environment. The same restriction also applies to alchemy treated Glowcaps.
Cost: 1 gp each. If treated as spell components, 10 gp per dose.