Nihil/guide

Fox
Go west and warp to Lake World. Take the boat south and east until you reach the bottom of a large island filled with trees. Enter between the gap in the trees. In the next area, head north and enter the log cabin. Interact with the fox pelt.

Dreamcatcher
Go east and warp to Totem World. Head northeast while avoiding the Noppera (you may wish to use the Fox Effect to make this easier), and enter the teepee. Interact with the dream-catcher.

Wings
Go northwest and warp to Crystal Tree World. Head southwest and ascend the green flight of stairs. Enter the building. Take the middle path on your left. Interact with the floating cluster of crystals.

Monochrome
Go south and warp to Game & Watch World. Head northwest and enter the house. Continue right past the burning building and enter through the next open doorway you reach. Interact with the handheld console.

Maple Syrup
Go northeast and warp to Autumn World. Head west, south, west again, then up between an opening in the trees. Interact with orange blob.

Noppera
(The Match and Wings Effects are required and recommended, respectively.) Go northwest and warp to Crystal Tree World. Head southwest and ascend the green flight of stairs. Enter the building. Take the topmost path on your right, then take the stairs and descend the darkened staircase. Equip and use the Match Effect before continuing down. In the next area, go southeast. Pass through the oval between two circles which otherwise look like two eyes and a mouth. Immediately equip and activate the Wings Effect upon entering the next area to stop the Noppera throughout. Navigate through the maze until you reach a black platform. Interact with the Noppera head propped up on a pole.

Rain Mask
(The Match Effect is required.) Go south and warp to Game & Watch World. Head north and enter the opening in the grove of trees. Continue north and fall down a hole. Carry on right until Yorutsuki is facing north, then equip the Match Effect. Go up until you see a red-orange path to your left, follow it to the Cryptic Tiles Maze. Navigate your way north and east to a down staircase somewhere in the middle of the maze. Interact with the rain mask.

Match
Go southwest and warp to Notebook World. Head south and west a bit to a black dot with the word "way" above it. While standing upon it press the Z key to be teleported to a burning area. Interact with the match in the center.

Lab Coat
Go northeast and warp to Autumn World. Head west and pass through a line of shoots. Go south and right a bit and climb up the towering stalk. Continue climbing up and left until you reach the next area. Enter the automatic door. Interact with the lab coat hanging on the wall.

Planet
(The Lab Coat Effect is required.) Go north and warp to Chess World. Head northeast and cross a black-and-white tile between two pieces. Go around and out along the path to Go World. Head south and east down a square hole. Navigate through the next area to the rafters above the entrance platform. Enter the train and head left to a dark red locked door.

OR

Go west and warp to Lake World. Take the boat east and jump into the depression in the center of the island. While avoiding the Noppera, make your way to a rusty U-shaped pipe. Go through it and south along the path. In the next area, head up and enter the train and go right to a dark red locked door.

Equip the Lab Coat Effect to unlock it. In the next area, take the second staircase from the right and enter the spaceship. Inside, interact with one of the two levers and wait a few minutes until the craft comes to a stop. Continue right across the surface of the moon to a building. Inside, interact with the floating ring off the edge of the platform.

Cloud
(The other ten Effects are required.) Follow the directions to the Planet Effect, but take the first staircase nearest the train instead. Use the Lab Coat Effect to enter a smaller spaceship and interact with the single lever at the front. Wait a few minutes until the craft comes to a stop. Exit south to the Cryptic Tiles Maze. Somewhere to the left is a second staircase. In the next area, you will encounter ten rooms which require a specific effect to successfully clear. Once you've crossed all the rooms, follow the stairs and interact with the cloud on the landing.