Lunarite (DnD Other)
From D&D Wiki
Lunarite is a mystical metal that is liquid during the day, and solid during the night. While in liquid form, it has the look and consistency of mercury, and depending on how much there is, it will either crystallize, or just solidify at night. If you just leave it out in a puddle, it will crystallize, but if you put it in a mold, it will solidify, Oddly, it's not based on time of day, and it's not based on sunlight hitting it, it seems to know exactly when the sun has set, and, no matter where it is, it will turn solid when the sun is gone. It can be used as a poison, if you tip an arrow with it, or put it in someone's drink, then it will enter their blood, or their stomach. When the sun sets, it will crystallize inside them, puncturing their insides, and killing them. You can use it as an alloy for a weapon or shield, making it weak during the day, but powerful during the night. If anyone has more uses for it, feel free to edit this page!