It was just like his old stone, only it had a swirly green glow to it and was slightly sticky with green mucus noticable when held for too long.
The Imp Stone worked slightly differently than the wishing stone. When a wish was made, rather than granting it right away the stone would create a miniature, invisible flying imp that would follow the wisher around.
When very first summoned, the Imp would grant the original wish of the user who had just made a wish creating it, in perfect clarity.
From there on the Imp would stick around the user, invisible to anyone but them. However given time the Imp would repeat the same wish again and again, perhaps just slightly differently each time.
Over time it would happen often, with the Imp granting more of the same original wish, but repeating it more differently and drastically over time. Eventually the wish may be so twisted it's just a chaotic distortion of the original wish.
A wish for a 100$ might screw the whole world's economy over. A wish for a simple body swap, might lead to the whole population's mind and body and different parts switched. A wish for an apple might lead to giant mutated fruits attacking the world.
It takes time for the wish to be corrupted gradually over time when it's repeated, but if a new wish is made the counter is 'reset.' If someone else makes a wish, the imp attaches the that person and locks onto their wish instead, and can only do that to one at a time luckily. However this means new wishes must constantly be made or the old ones will get heavily out of control.
