Right after you fight the dark wizard, a door (Previously locked by the wizard's magic) will now be accessible. Past the demented puppets and a door ahead there will be a hallway off to the right, the first door on the left in this hall is the doorway to an empty room (That's what I thought...) Find the very small hole on the north wall and equip "Lord Myu's Amulet. You will see a green panel in the ceiling. Shoot a bolt or arrow into the hole and climb up the staircase that lowered. Earthquake awaits, a powerful 2 hand hammer that causes slowness.