Mario Maker 2's Secret of the Dry Bones Shell stage is a late-game level in the story mode and easily one of the most difficult in the game.
As the name suggests, it revolves entirely round using a Dry Bones Shell - which has various clever uses that allows you to get past all manner of deadly traps.
The level plays out as a series of rooms, each with their own challenges and ways of using the Dry Bones Shell to best them.
How to beat every challenge in Mario Maker 2 stage Secret of the Dry Bones Shell
The first room is the most skilled-based but simplest to complete. Jump into the shell and holding jump (the B button) you can bounce off the Boos and the gears to get past the lava. If you're struggling with the gears, try and hit them on the right-most side to propel you that much further.
The second area has a locked door on the right and a door you can enter in the middle. To reach the block on the upper left, jump then press a shoulder button to leap out of the shell in midair to get the 1-Up Mushroom inside.
Go inside the room. Here are three red coins you need to collect to get a key. You get them by doing the following:
Lower-left coin: Ground pound (press down while in mid-air) the ? block on the left using the Dry Bones Shell to make the vines travel down. Jump out of the shell, climb down the vine and get the coin.
Lower-right coin: Enter a Dry Bones Shell and fall off the edge holding left. Leap out of the shell (press a shoulder button) to grab the coin on your way back up.
Upper-right coin: Leave a Dry Bones Shell underneath the platform by pressing a shoulder button. Now enter another one that spawns from the pipe on the left, and bounce from the discarded shell to give you the elevation you need. Now grab the coin.
With all three coins collected, head through the door to the previous area so you can use the key on the door.
You'll now arrive at a checkpoint and an optional 30 Coin piece in the upper right. To get this, Dry Bone Shells will spawn on a regular basis from the pipe. You have to leap out of a Dry Bones Shell just as one falls at the same height as the coin, seeing it bounce from you and hit the coin. The timing is tricky, but keep trying and you'll get it.
When you're ready, head through the door on the right.
The following room has a giant Thromp on the right. To get past the Thwomp, ground pound inside the Dry Bones Shell so it'll travel through you. You can also ground pound the ? block to get a 1-Up Mushroom that'll bounce from the music block to your level.
Head up the end platforms to reach a cog blocking the way to a key down below. Above the cog are two platforms - which you can reach by holding jump and bouncing from the cog - that'll fall when you stand on them. If you stand on one, then ground pound and hold down, you'll collapse and travel through the cog uninjured. Now grab the key, bounce over the spikes and into the door.
The next room has a Boo with a Piranha Plant above it on the far side, and several cogs and conveyor belts below. Turn away so the Boo moves towards you until it's over the nearest cog, then when riding the Dry Bones Shell, bounce onto the Boo (not the plant above!) so the plant drops onto the conveyor belt below, and bounces up next to two cogs and a POW block.
Now stand to the left of these two cogs, leap out of the Dry Bones Shell and kick it right.
It'll travel over the plants - including the one you've just added - until it hits the POW block, destroying them all and giving you access to the pipe on the right.
The final room is the easiest of all - hop into the Dry Bones Shell and float over the lava to the right when the crusher is out the way.
At the end, jump then leap out of the Dry Bones Shell to reach the ledge above, then hit the axe on the right to complete the level.