Full list of all 32 The Explorer Of Night achievements worth 4,000 gamerscore. It takes around 0-0.5 hours to unlock all of the achievements in the base game.
The base game contains 17 achievements worth 1,000 Gamerscore, and there are 3 DLC packs containing 15 achievements worth 3,000 Gamerscore.
Don't get lost in the dark
You have defeated the final boss
...
Don't get wet
Fix the platform mechanism
Destroy a pike
Beware of the pikes
You have defeated second boss
Thank you for playing
Use dynamite for its intended purpose
Find the key and open the door
Run away from the stone
You have defeated the first boss
Find and use a gear
Use any weapon to stop the enemy
Jump on the frog
You have passed first level
Move the block
You have passed second level
Get over the platform
Jump over the first fish
Climb a ladder
Jump on the mushroom spring
Pass the fourth level
Drop the block
Get across the first waterfall
Pass the third level
Complete the sixth level
Jump from one collapsing platform to another
Overcoming the section with accelerated platforms
Complete the fifth level
Get through the first obstacle in the tunnel