This seemingly ordinary marble is very susceptible to air currents as though it were only a fraction of its true weight. When placed on a flat horizontal surface, such as the floor of a room or chamber, the marble rolls in the direction of the current path of air currents around it. The marble has 1 charge. You can use an action to speak its command word while placing the marble on a flat horizontal surface, expending 1 charge. The marble rolls towards the direction of the nearest exit of the chamber it is placed in, ultimately coming to rest against the nearest exit (regardless of air currents). The delicate calibration of the marble is destroyed and it becomes a mundane item.