Here is the full list of all 38 Moss achievements.
Finish the first book of Moss.
Defeat the serpent Sarffog.
Climb to the castle bridge alongside Quill.
Use your power as a Reader to break many objects.
Collect a large amount of Relic Dust.
Guide Quill to destroy multiple thorn patches.
Enter the Namelhook Mining cave alongside Quill.
Enter the Abandoned City alongside Quill.
Destroy a Forged enemy with a controlled Scorcher.
Take control over many Forged enemies.
Unlock the path to the Mire Temple's altar room.
Light the torches of the Knights of the Sun.
Give Quill a high five.
Collect a small amount of Relic Dust.
Use a Screecher to unlock the path forward.
Enter the Mire Temple alongside Quill.
Defeat the Screechers first encountered in the Mire.
Use your power as a Reader to heal Quill for the first time.
Startle Quill from behind.
Follow the Starthing and Quill into the impassable Mire.
Enter the Clearing alongside Quill.
Discover your first Forgotten Piece.
Collect all of the forgotten fragments.
Collect all of the Relic Dust.
Annoy Quill by delaying the adventure.
Destroy a Forged enemy with an aerial attack.
Find a low-hanging path to the town pub.
Destroy two or more Screecher enemies with a controlled Ticker.
Rescue Argus without a single death.
Break everything within the town pub that can be broken.
Use Quill's sword to cut down a lot of grass.