In the Smokehouse, use the Dark-Light Device to uncover a towel on the right side of the room. Yank on it to reveal the first hidden gem.
Once in the Fishing Hut, turn to the left and use the Poltergust 5000 on the ground. If positioned correctly, the second gem will roll out from under the floorboards.
Once you have entered Under the Ice, grab the Blue Toad and bring him up to the higher level. Blast him through the hole at the top to have him slide down and bust the third gem out of the ice.
In High Wires, make your way to the second platform by using the gondola. Once there, use the strobe light on the two birds and the nest to reveal the fourth gem.
After you enter the Airway through the door in the Terminal, use the telescope and spy on a bird within the icicles. The bird will move, carrying the fifth gem and dropping it in a bin down below. Later in the mission, head to the same bin to find the gem.
In D-2, head back outside to the Chalet Approach and head to the left where the grill is. Without removing the turkey on top, activate the grill and let the turkey burn. Grab the flaming turkey and bring it over to the frozen portrait near the snowman. Once melted, use the Dark-Light Device to uncover the sixth gem.
In the Prospector’s Crossing you’ll notice the seventh gem wedged within the ice on the floor. Unfortunately, Blue Toad is no longer with you so you’ll need to find a replacement to help break the ice. Spin the axe on the right wall to reveal a piece of wood. Use the wood to crack the ice and free the gem.
When sliding down the Skip Slope, take a left and go through the opening in the spinning wheel at the second fork in the slide. The eighth gem will be on this path. The spinning wheel might not be spinning at the right time to allow you through, so it might take you a few tries to get in.
When riding down the shaft, make it to the bottom, then pull on the chain waiting there. This will open a hatch above, so have the shaft go back up until you see the ninth gem.
Once you make it to the deep hall and you have the coal transported from the Pit Mine, have one of the coals placed under the fire. Use the burning coal to target the tenth gem lodged in ice above. Have it melt and collect your gem.
In Crossroads during D-3, go through the portal device and use the Dark-Light Device to uncover a wagon. The Spirit Balls will move to the other side of the gap, so run through the portal device to collect them. Return to the location of the wagon and give it a shake to get the eleventh gem.
If you go to the Crystal Quarry in D-3, enter the portal device to be transported to the Chalet. The portal device will drop you off, revealing the twelfth gem in the process.
When you finally make it into the Gondola, use the flaming nut shooter to melt the ice holding down the tree on the left, then shoot it again to have it tumble over. Make it over to the area and cross the giant log. Enter the outhouse to be transported to an alternate dimension where you must shoot snowballs at three different hiders within 60 seconds. If you defeat all three in time, the thirteenth gem is yours.