Dwarf Mine is a challenge that featured in the fifth series of Raven. It is set in an abandoned mine and played by two warriors (normally 1st and 2nd place). First they must kick down the planks barring the door. One goes down a long tunnel where they find a wall with four irregular symbols on it.
They must now describe them to their partner who is in a room full of support collums, each with a symbol on. The warrior must find the matching symbol, and knock down it's pillar. Underneath is the ring. If they knock down too many incorrect pillars, or take too long, the mine will collapse, trapping them inside and costing a life.
But if they get get all four rings they keep them, and their lives.