Instructions
Play through the game until you get to the Phantasmal Bog in Kolima Village. This is the area where you wake up just after you encounter the Dream Tree.
Follow the circular path from the beginning area until you reach a rock that you can push into the bog. Push it, then exit the area to the south.
Walk along the path to the lake, then head north, where you will see a puddle. Cast Arid Heat on the puddle, which will dry up the lake. Return to the lake and move the logs in that area to get to a second lake.
Drain the water from the second lake and then push the logs aside. Refill the lake, then cross the path you made from the logs to get to the south bank. Exit this area.
Freeze the puddles in this area, then move the logs onto them to make bridges. Cross into the next area. Push the log into the water below you.
Slide down to the next level, which has a leaf you need to freeze. Go right, down,
up and left to reach a new area. Pass through this area to the south.
Walk along the linear path and push the block out of the way. Melt the ice blocking your path, and then push the next block into the water to open up a path to a door. Save your game and pass through it to initiate a boss battle with Sludge.
Defeat Sludge and you will wake up back in Kolima Village. When you wake up, there will be an item on the ground adjacent to you. Grab it to get the Crush Tusk.