Instructions
Enter Mount Coronet from the eastern entrance, which is accessible via Hearthome City. Walk over to the western side of the cave, then head north to a pool of water.
Surf across the pool of water to get back to the eastern side of the cave, then ride up the wall using a Pokemon that has the Rock Climb ability. Go up the stairs at the top of the wall.
Head west, then south until you find a stone that you can move with the Strength ability. Push it down until you can access the stairs. Cross the bridge, head down the stairs, cross under the same bridge, then go up a set of stairs to another bridge.
Cross the long bridge to the eastern side of the room, go down the stairs, then head through the door at the northwest end of the room. Follow the linear path in the next room to get to a new area.
Go north, west, then south to find an exit from Mount Coronet. Take either path to the east, then ride up the wall using a Pokemon that knows Rock Climb. Walk through the grass to the west and enter the cave to go back inside Mount Coronet.
Climb up the rocks, then go north and east until you reach another exit door. Walk to the east and go down the stairs to a small valley. Stand in the square of grass and climb up the western wall using Rock Climb.
Follow the linear path all the way to the west and enter the cave at the end of the path. Head east up the stairs, then go south and west up another set of stairs. Go north from this area through an exit from the cave to Spear Pillar.