'''Sol stones''' are [[valuables]] with negative volume and mass, making your load lighter just by being in your inventory. A natural onyx sol stone has a mass of negative 1000g, but it is possible to use a [[scroll of change material]] to change it into a negative volume of some very dense material, creating a larger negative mass and reducing inventory weight even further. Keeping a few sol Sol stones can be stored in a container "unfills" itto reduce its weight, making space for other itemsbut they do not add room to a filled container.