Soul Gem (1/2): Fryno
When you reach Typhoon Trail, drop off the cliff to your right. Enter the cave here to exit from another cave near the level start. Follow the trail here to grab the Soul Gem you passed by earlier.
Soul Gem (2/2): Trap Shadow
Proceed to the Battle Gate at the end of Ice Break Atolls. Before heading through the gate, look for a little inlet between two trees. Follow this narrow path into a hidden area of Perilous Precipice (prepare for more exploding snowmen robots), and you'll find this Soul Gem at the end.
Soul Gem (1/3): Blast Zone
At the level start, you'll pass a burning gate. Just a few steps later, you'll turn on a water pump and acquire water balloons. Bring one back to this gate to clear the way, then follow the platforms beyond to reach a Soul Gem.
Soul Gem (2/3): Freeze Blade
When you pass the first flaming gate in Birchberg, hang left. Hop up the platforms here to reach another Soul Gem.
Soul Gem (3/3): Scratch
When moving through the explosive barrels in Forest Path, take a left at the flame jet. Quickly hop across the other flame jets here to reach the level's last Soul Gem.
Soul Gem (1/2): Punk Shock
When you receive the sheep disguise from Softpaw in Sheep Inspection, use it to climb the stairs to the left. There's a Soul Gem in this small area.
Soul Gem (2/2): Doom Stone
When you enter Glob Lobber Gangway, make a left and follow the staircase up. Traverse the long series of platforms it leads you to, and you'll find the game's final Soul Gem.