Dawn and dusk are the perfect time to spy the crystures. The magic stored in old gemstones can find its way into all sorts of life, imbuing it with odd properties.
As gemstone’s stores and energies can be reset or changed by exposure to moonlight and daylight, it is doubtful a crysture would be seen at those times. These creatures amble about the half-light, enjoying the quiet.
Never has a crysture been a familiar. Perhaps it would be too powerful in the hands of a mage.