Make sure Ox is leading the party throughout this route. You should first knock down the wall north of the staircase you came from. Follow the path north and continue straight where you should come spot another weak wall. Knock it down, and proceed forward. You'll then spot two weak walls, one to your right, the other to your left. Knock down the wall to your left, and continue heading north. You'll come across two northern paths on each side- one to your right, the other to your left. Take the right northern path and break the wall you encounter. From this point, head east and then south. Break the next weak wall you come across, and head north. Heal up when you reach a staircase, and when you're ready, head downstairs.