Here is the full list of all 33 Castle in The Clouds DX achievements.
Defeat the Ice Queen
Defeat the Scylla
Defeat the 500th enemy
Defeat the Poltergeist
Got the first ability
Defeat the bandits
Defeat the 200th enemy
Take the first heart
Level up for the first time
Defeat the first enemy
Defeat the Lamia
Defeat the pirate queen
Defeat the succubus
Defeat the dragon
Defeat the death
Defeat the Ancient queen
Defeat the core
Lost treasure
Got a treasure
Got all the treasure
Bad, good, best, see all three endings
Make map reach 100%
Defeat the 1000th enemy
Level 50
Level 100
Got all abilities
Use thief after clearing
Use fighter after clearing
Clear without taking the heart
Take all the hearts
Level 200
Own all weapons
Got Excalibur.