On world 53 or 69 (or anywhere if you can find other players), visit Port Sarim, south of Falador, and go to the second boat from the south. Talk to the Squire, and agree to visit the Void Knight's Outpost. [10] Once the minigame starts, try to destroy all enemy portals, or ...
To get out, go out of the room and keep going until you get to a wall. Push on it and it will open. Keep going until you get to a room with lava and Lesser demons. Climb the rope there and you will be on Karamja island. Go to the dock and get a ride back to Port Sarim....