Unlocks: Flame Slinger’s “Super Volley Shot” Ability
Just after crossing the bridge in the Underground Lake, you’ll be in a passageway with crystals and cracked rocks blocking various paths. Use your pickaxe to make your way through the first on the right.
You’ll come across a crystal-blocked path. Remember this location for later.
Later in the level, you’ll open a locked door that guards bombs. Grab one and run back to the path blocked by crystals.
Make short work of the crystals and head up the slope to the left.
You’ll come to a pretty hefty block-and-cannon puzzle. To start, push cannon A to the right twice. Fire to destroy a set of crystals. Push cannon A to the left once and do the same to rid yourself of more crystals. Now push cannon A to the left twice and fire once again to destroy a third bunch of crystals.
Walk counterclockwise around the blocks and crystals for a new view of the puzzle. Push block A down once, and then once to the left. Push block B to the left once as well.
Push cannon B up the tracks, and fire to destroy the two exposed sets of crystals.
With a few more obstacles gone, push block C forward into the wall. Then push block D back once. Block D was blocking another set of crystals. Line up a shot with cannon B and destroy it.
Walk around the puzzle to cannon A. Push block E once to the right to expose another crystal batch. Destroy it with cannon A. Then walk forward to block F. Push it once to the right to expose yet another set of crystals, and use cannon A to destroy it.
Now walk up to block G. Push it down once to clear the tracks for cannon C.
Run to the opposite side of the puzzle and return to cannon C. Line it up with a final set of god-forsaken crystals.
Destroy that sucker and claim your Soul Gem prize behind it. You’ve earned it.