Here is the full list of all 30 Downward achievements.
Build four different rooms in the Merchant's Lair.
Unlock all Meditation skills.
Get 10 Gold medals in the Challenges.
Obtain 2000 Skypieces.
Perform 500 wall-runs.
Perform 500 slingshots.
Obtain 1000 Skypieces.
Survive your own recklessness.
Perform 500 double jumps.
Unlock all Wisdom skills.
Buy all the upgrades of the Old Man's Room.
Unlock all Insight skills.
Unlock all Endurance skills.
Sell 15 items to the Merchant.
Obtain the Slingshot Artifact.
Gather 50 Dry Artifacts.
Die from a Drone explosion.
Perform 500 wall-jumps.
Unlock all Pursuance skills.
Sell 5 items to the Merchant.
Reach the temple on top of the cliff.
Gather 25 Dry Artifacts.
Obtain the Double Jump Artifact.
Obtain 500 Skypieces.
Exit the tutorial area.
Get a Gold medal in the Challenges.
Defeat your first golem.
Use the Mark for the first time.
Die from a Cactus.
Wake Up!