Minecraft wiki entry for Creating_a_challenge_map, associated text: Buried alive: Make a funbox out of falling sand or gravel spawners. (Add the rare anvil.) Fill the large room with sand. Give the players some stone shovels. Add blockades to the room. Set the spawning cooldown to 4 ticks minimum to 5 ticks maximum. Set the current spawning cooldown time to 4 ticks. When players dig up the sand, the room will rapidly start to fill up with sand and then they will die! Give them one torch each to remove some of the gravel.