Here is the full list of all 20 9 Days achievements.
Clear the insects from the castle.
Open a chest for the first time.
Defeat the threat on the Ninth Day.
Defeat the Guardian of the planet.
Defeat Mudaris ex student.
Defeat the Forest ruler.
Defeat the Giant on Balu Planet.
Defeat the mysterious fighter.
Discover the Divine City.
Go to outer space for the first time.
Destroy a planet for the first time.
Destroy a settlement for the first time.
Control the Omen form.
Fly into a blackhole.
Discover Planet Balu.
Discover Planet Tunda.
Captured by the Guild of Assassins.
Captured by the people of Tarnished Tribe.
Finish Level 3 of the Void Realm
Use the Ancient Forge