The characters will come across a puzzlebox which can only be opened with the answer to this riddle:
All around the world are known
Two castles made of wood or bone
Which seldom are left all alone,
for often are the castles thrown.
To each’s six square walls you ride
To ask the nobles found inside
The twenty one in each decide
With whom will fortune’s grace reside.
One final word, you must beware!
Consult these castles with great care.
Within the two a vicious pair
Will trap by chance with snake-faced snare.
Here's a hint that the players would know, but that you don't need to solve the riddle:
The answer is a four letter word.