|from Mulan (1998)|
The party finds a 12" high wooden cage (complete with a mini pagoda roof and a metal loop to secure to a hook) containing a three or four inch high, brightly coloured, cricket.
The creature is clearly magical in origin, but it's powers may not be immediately clear.
Anyone who carries the caged cricket with him will be gifted with incredible luck.
Namely, any natural rolls of a one (be it on a save, an attack roll, even damage) may be immediately rerolled (and the result of the second roll must be taken - even it's another one).
If released from its cage, the cricket will dart off at supernatural speeds, never to be seen again, and its magical influence lost.
The power also vanishes if the cricket is killed (e.g. some smart ass might try to eat the cricket to gain the luck power permanently; although the Dungeon Master could rule, in this case, that the cricket's natural luck allows it to survive its complete passage through the character's digestive system and ends up causing him some unfortunate damage when it angrily erupts out his arse!)
It's also up to the DM to determine what inconvenience, if any, the owner of the cage suffers while he is carrying it. While not heavy, it is clearly a nuisance when considering going into combat, climbing rock faces etc
The cage must be on, or very near, his person to gain the magical benefits. If it's set down (e.g. on a shelf or table), the magical benefit is lost until the character picks the cage back up.