Mystics and iron
Optional rule: Ferrous metals have strange properties that inhibit mystic energy. A mystic who wears any form of iron or steel becomes unable to control the raw flows of power that otherwise come forth so easily. Any iron object that forms an unbroken band around a portion of the mystic’s body causes this type of disturbance—including shirts, pants, shoes, necklaces, helmets and headbands. Even rings and hoop earrings make utilizing mystic magic impossible. Only very small items such as stud earrings do not pose problems, since they do not encircle any part of the mystic’s body.
Note that arcane spell failure chance does not apply to mystics. There is no such uncertainty with the mystic system—a mystic who is bound in iron is totally unable to utilize his magical talent.