From Lost Fables Wiki
Moondrops are like shining silver liquid, which beads up and runs like mercury. In fact, it is very easy to mistake for mercury, with the exception that it is practically weightless, and faintly glows, especially at night and in the moonlight. It is said that drinking 100 doses of pure moondrops, a full liter, will lengthen your life by an age, though this is mere speculation.
Gathering moondrops requires a large, tent sized layered tarp made of mystic hemp with ice salts lining the inside. If this tarp is spread out in the air during the last days of an age in a place with a clear view of the moon, moondrops can be gathered. While on the bottom side of the tarp normal condensation will form, on the top side Moondrops will form, and these precious few drops must be gathered up before the first rays of sunlight strike them. For every ten square meters of this tarp, one dose can be generated per age.
Moondrops have no real mundane use, though they taste delicious, much like a slightly more citrusy lemonade. Each swallow manages to feel like the first drink of water to an extremely parched throat, and they're about 6% alcoholic. Most describe drinking moondrops to be one of the best experiences in their life. When used in alchemy, moondrops supercharge the effect of any potion they're in, making it twice or even three times as effective as normal, though they can only be used on a second-stage mixture.