You've got to achieve this:
- Remove the 3 ice blocks (use the flame monster).
- Make the fireballs destroy the bombs on the left.

Make the stonehead break the marked skull block.
Then release the flame monster to remove the 3 ice blocks.

Prepare the place for the fire breathers.
Remove 6 blocks and 8 blocks using the hammers.
Then enter the cyan teleport.

Touch the blue key to make way for the fireballs.
If you've done everything right they will shoot the bombs.
Hint: You can stop the fireballs by touching the blue key again.

Make the stonehead break these 2 blocks.
Then release the flame monster to break the ice blocks.

Now you need one fireball at the correct position
to break the blocks containing the mystery.