When you reach Perilous Plateau, took a right from Sharpfin and head up the slope to find this scroll.
After encountering the Boom Bosses, bust up the boxes in the back of the area. Follow this hidden path to find the first ducky.
You'll spot this as you approach the second platform with a rotating electrical rod. Proceed through, then take a left at the next platform to reach it.
Take a left before exiting Arid Cave to grab this off of a ledge.
Before destroying the second crystal, continue up the platforms past the screws. You'll find this a little higher up.
When you land in Underground Lake, you'll be near a dual Undead/Earth Elemental Gate. Use a Swap Force character with these elements (or use appropriate Skylanders, if you're playing co-op) to open the way. Complete the challenge inside to earn this.
Take a left after crossing the long green bridge in Serene Walkway. This leads to the last duck.