A combination lock, possibly to open a chest or door or other entry point. A magical puzzle, for those interested.

Checkerboards on floors of dungeons... is there any greater bane to adventurers?

'It is a door, a stout wooden door with its frame, just standing there in the middle of the field. Why would someone put it there? And the important question, does it actually open to anything?'

Journal of Thomas Mccannon.

If the adventurers are smart, they can solve this riddle and get the information they need.

Then suddenly all your body paralizes and you hear a voice echoing in the distance "seems like another rat has been lured to my maze," this voice was terribly cold but playfull, "come on you are not already planning on leaving, the fun has only begun."