Magical item-Shadow ring
Appearance: a ring made out of black metal. It has a ancient symbol of shadow on it engraved.
Ability: the wearer of the ring can turn into black dust at will and can travel much faster than normal. Also he can decide if just parts of his body or everything goes in that state. So he can change his legs to move faster but let his upper body stay in a normal state to use weapons and fight. Bullets are useless at the wearer.
Side effects: if the ring is worn too long, the skin will change the color to a more grayish. Also it will be a personality change if the wearer isn't good enough. At end it can cause death. If the wearer has enough will power (which is rarely) he or she will survive but will feel no hunger or thirst for ever (wearer can't be stimulated, everything will taste awful).