Two sets of three tokens face each other on a line in the wall. There is a token sized space between them and the tokens can either move forward or leap frog the token in front of them if there is a space beyond it.
Inscribed inside the inset hexagon at the center of the room in gnomish is the puzzle:
“I and two other gnomes came upon another group of three gnomes while traversing a narrow ledge over a deep crevice. We wished to exchange places, but had only a gnome of space between the groups and it was unsafe backup. A gnome could safely step around a single other gnome if there was space on the other side. How did I surpass this obstacle?”
In an unbreakable crystal case are 6 keys one of which shatters each time the puzzle reaches a point where none of the tokens can move forward and the tokens are reset.