After you make your way through the cave east of Miracola, you battle Magma the Fierce.
Location of Magma the Fierce
Magma the Fierce is found at the end of the cave east of Miracola.
How to Defeat Magma the Fierce
Carefully avoid the fireballs that Magma the Fierce shoots out, and also avoid the spinning flames, then jump onto the tile just southeast of Magma the Fierce. This makes a switch appear. Jump onto the switch to remove the rounded tile to the east of Magma the Fierce.
Then carefully jump onto the northwesternmost tile to make another switch appear. Step on that switch to make the other rounded tile disappear. This makes Magma the Fierce's platform disappear, and Magma the Fierce will fall into the water and die.
Moving On
Go east to the next room, then go up the two flights of stairs, then go north to exit the cave and reach the third overworld area of Chapter 3.