Before the county of Corvis, there was the Wizard Corvus. Thirteen hundred years ago, a mad powerful wizard had an estate in the area that became the county of Corvis. Over his 800 year span, he created thousands of magikal items of various types and power level, some of which survive to this day.
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).