The Cascading Vortex
Stats needed.
The Cascading Vortex is a light which was (is?) carried by the Mist Dragon in Knights of the Round.
The standard conjecture is that the Cascading Vortex is programmed so that only one can exist at a time, and when it is lost, a new one will be dropped by the Mist Dragon. But this is only a conjecture, and very little is known for sure about the light. It is suspected that the light has a less than 100% regen rate, and that failed regens are what trigger the Mist Dragon to drop new vortices.
At one point, the Vortex was scrapped, and this led to a race to the Mist Dragon, where it was successfully recovered.
At one time there were (are?) two Cascading Vortices. Consistent with the above conjecture, this is believed to be because of a bug in Knights of the Round.
Perhaps tragically, the item virtually never was (is?) used in practice, largely for fear of loss.