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