Riverbond

Important information to start: There are more than 35 skins to find throughout the game and the 3 extra skins you start with do not count towards this achievement (Donut, Watermelon, and Pug).

Edit: With the addition of the 9th level and King's Garden this achievement is even easier now. There are 8 skins in King's Garden and I found 10 skins in level 9 Crystalwatch. However I will leave this guide as is with only covering the tutorial and original 8 levels as none of the new skins are necessary for the achievement, but are easily located if you need them.

You will find skins throughout the game inside golden chests. They are one time pick-ups, the chests will drop coins and gems when opened on subsequent playthroughs. Sashamorning has a great guide for a work-around if you don't feel like following this skin location guide.

Also I did my best to find every skin I could during my playthrough but I'm sure I missed some. If you find one not in this guide or feel that any of the locations need better clarification please leave a comment and I will make the necessary changes.

Tutorial
Nigiri Area 1 Just before the exit portal, hard to miss
Maki Area 2 Just before the exit portal, hard to miss

Restwater Valley
Pinky Area 1 (Ancient River Cabin) When you see the exit portal follow the path up and to the left (NW)
Eggplant Area 2 (Clever Clan Homestead) Directly north of the boat you use to leave the area
Mr. Crabby Area 3 (Ochre Beach) After going up the waterfall to the last crab nest head east
The Kid Area 4 (Village of Gathering) Right before the exit portal

Wailing Mines
La Banane Area 1 (Vertella Wood Shore) On the ship just to the left of where you start
Bob the Manic Cat Area 2 (Old Trading Post) From where you start follow the path and take a left at the fork. Go through the gate and then past the horde of pigs is a large structure. The left most area of that structure has a huge pile of crates, barrels, and food under it. Keep destroying that stuff until the chest is visible
Juan Aguacate Area 2 ( Old Trading Post) To the left of the exit portal is a ladder leading up to a platform with a chest
Lucky Cherry #2 Area 3 (Windmill Hills) Following the path from where you start you will quickly come to a windmill. To the left of the windmill is a small ledge leading to a chest
Zouizoui Area 4 (Whispering Cave) Follow the linear path through the breakable wall. When you reach the broken bridge going southeast take the northwest path. Next to the captive you need to rescue is a ladder up to Larry the Lost and the chest

Hogmarsh Hollow
Mr. Mounty Area 2 (Swamp of Eternal Drench) When you get to the end of the area and see the 2 treasure piles and the exit portal, just east (right) off the edge of the map from the treasure piles is a chest
Bacon! Area 3 (The Neverglade) Directly next to one of the password fragments, hard to miss
Demelza Area 3 (The Neverglade) Just to the left of the exit portal
Monkawanka Area 4 (Industry Town Porco) You'll come to a house where you have to use a silver key to enter the front door. On the outside of the house, left side, is a ladder that leads to a path to the roof. There's a chest on the highest roof of the house
Bucky B Area 4 (Industry Town Porco) Inside the previously mentioned house (where you get the Leather of Intent) on the second floor, the left most rooms chest

Stonefrost Peak
Sour Tooth Area 1 (Snowy Pass) Chest is directly next to one of the puppies you rescue and behind a log, hard to miss
Lover Mu Area 1 (Snowy Pass) Go northwest (up and left) from where you spawned and you will see an exit portal in the side of the mountain, it leads to an area with a bunch of enemies, a star, and this skin
I Am Walrus Area 2 (Abandoned Boneyard) While looking at the exit from this area follow the wall either left or right, both ways will have ledges you can climb to get up on top of the wall here. The chest is on the left most portion of this wall
Preppin Area 3 (Ice Palace Courtyard) To the left of the exit and where you kill the giant minotaur to get the silver key is a chest "hidden" inside 3 trees
Boombox Area 4 (Lower Ice Palace) From the exit follow the wall left and break the railing, hug the edge to get around the corner and up the right ladder to a chest

The Sandwall
Kolala Area 1 (Sand Dunes) From the exit follow the right side edge of the map and you should see a chest hidden inside a bunch of bushes. If you're coming from the other direction it's right behind Marty McHam
Robot 05 Area 2 (Cliff Face) From the exit, go right until you see the Hydrocactus seed you need to collect on the edge, then go directly down from that to see the chest on a lower ledge
Taco Area 3 (Watering Hole) From where you spawn, follow the right edge of the map until you see a lower ledge you can drop down to
Baaily Area 4 (Flooded Cliffs) Directly to the left of the exit you can either climb up or ride a waterfall up. The chest is up here next to where you plant one of the Hydrocactus seeds and get the Talk the Talk achievement for speaking to Hamdini

Lost Museum
Avocado Area 1 (Desert of Solitude) Left of the exit up a ledge
Bullet Kin Area 2 (Museum of Ancients) Right of the exit and next to one of the Book of Memories you can see a ledge and ladder behind some boxes and the railing. Break everything and climb the ladder for a chest
Mooey Area 3 (Ancient Courtyard) Just left of the exit behind the present, table, and crates
Mademoiselle Area 4 (Layered Garden Library) 4th floor (follow the waterfall up to the fountain, where the water doesn't go up any higher) go left and break the crates in front of the glowing door. In this area you get the Page Turner achievement, grab the left chest at the top of the area
Viking Area 4 (Layered Garden Library) Just to the left of the exit

Sky Garden
Cute Strawberry Area 1 (Azure Outskirt) Very linear zone. When you get to the last monument to clean, instead of going towards the exit go towards the bottom of the screen where you will see a couple islands you can jump across to a chest
Raz Aquato Area 2 (Gardens of Azure) When you spawn in this area go immediately down the ladder. Here you will find Spirit-Running-Softly for the Seek the Rainbow achievement, and the skin in the chest to her left
Pandoo Panda Area 3 (Old Wall) After crossing your first dragon bridge go right to see a chest out in the open
Uramaki Area 6 (Upper Treehouse) Small area. Climb the ladder and follow the upper floor around to the right
Money Cat Area 7 (Treehouse Rooftop) When you spawn in run left and jump up the ledges until you reach the chest

Ash Fortress
Pumpkin Area 1 (Front Courtyard) On the second level where you talk to the Eldra Spirit, behind her towards the exit is the chest, close to the left stair set
Shovel Knight Area 4 (The Banquet Hall) Enter the banquet hall and go left around the tables. You should see a ladder on the wall left of a fireplace. Take the ladder up and follow the path right to find a chest
Popcorn Time Area 6 (East Tower) After grabbing the Tower Dungeon Key and speaking with Eldra Highest of High for the Biting Tongue achievement keep following the top of the wall for an easy chest
Special Unicorn Area 8 (The Sanctum) Behind the Eldra Spirit, right of the exit

NOTE: This solution involves deleting your global saves. I don't know if it works with stars, but there are more than 35 stars in the game. Don't do this until you've gotten all of your stars.

Skins can be found in treasure chests around the world. Unfortunately, going back to chests you've already been to only gives you coins. I was stuck at 97% and couldn't find any skins.

I deleted all my saves and started going through the tutorial. I found the first two skins (Nigiri and Maki) in the tutorial (one in each world). But it didn't pop. And the tracker didn't go up.

BUT...

As I sat here typing up the beginning of a solution, the achievement popped in the menu. Mind you, it was a VERY late pop, but it popped. My solution, therefore, would be that if you are down to a few (and until someone compiles an actual skin location guide), go ahead and delete your global saves, run through the tutorial, and wait. It took maybe 4-5 minutes of me sitting here ticked off, but since it worked, I'm passing the information along.

Hope it helps. Best of luck!

Full Playthrough for anyone looking for videos.

The first 5 Mins of Lv.1 include an overview of all the achievements in this game pointing out tips, what to expect, and what to look out for...basically a walkthrough

All videos will include TIMESTAMPS (see below) of everything I found on my run and where to jump in the video if your looking for something specific, there will also be Achievement links pointing out when each level specific achievement is unlocked just under the videos.
- If there's no timestamp beside something it means that its in the same area as the one directly above.
- This (=) indicates every time you change areas/stages.
- This (-) Just indicates something found in the above area (=) before you leave.

Level 1 - RESTWATER VALLEY
Timestamps:

Level Specific Cheevos:


Level 2 - WAILING MINES
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Level 3 - HOGMARSH HOLLOW
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Level 4 - STONEFROST PEAK
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Level 5 - THE SANDWALL
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Level Specific Cheevos:


Level 6 - LOST MUSEUM
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Level 7 - SKY GARDEN
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Level 8 - ASH FORTRESS
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Riverbond Full Play-through Gameplay Playlist:
https://www.youtube.com/playlist?list=PLvrkjkOmqksopIiy01SJQ...

At the beginning of the second adventure, Wailing Mines, there is a chest that includes a skin up and to the left from start. Claim the skin, quit, and restart the adventure and the chest gets restocked with a different skin.