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