Minecraft wiki entry for Beating_a_challenge_map, associated text: Dig tunnels under the floor so that there is one block between the tunnel and the room. Every once in a while, mine a block above you and place a light-emitting block in the room above, before quickly sealing the opening again. This will disable most of the spawners and will make the Charge and Retreat method much easier. Using lava as the light-emitting block is very effective, but also dangerous.