Stones that have been attuned to the extreme temperatures of deserts or icy wastes. Such stones are quite valuable to adventurers as they can use them in order to preserve or prepare meals, make extreme environments bearable, and use them in clever devices.
Arune Spheres are hollow, blue reflective metallic spheres about 25 cm/ 10" in diameter (though some are larger). They are made of a thickish glass mirrored on the inside. When magical energies are flowed through the sphere, it produces a haunting tone, which can be varied by the type, intensity, and harmonics of energies passed through it. (It sounds like an electronic organ.) If multiple energy flows are generated, multiple sounds can be generated, some of which sound like mundane instruments. Masters of The Craft can replicate almost any sound in their memory with one. Though originally used as a training tools for those with The Power, it has been adapted to be a musical instrument. All it takes is someone with patience, medative training, and a touch of the Power, to use it. (Thus becoming the favorite instrument of anyone who was tested to the first level of the Craft, but failed to advance).