Here is the full list of all 28 AereA achievements.
Reach level 50 with any class
Retrieve the Baton
Retrieve the Drum
Poison an enemy
Complete all sidequests
Retrieve the Accordion
Retrieve the Bell
Retrieve the Sousaphone
Retrieve the Violin
Reach level 30 with any class
Use a skill 100 times or more
Hold 10.000 Clefines in your inventory
Retrieve the Lyre
Retrieve the Harp
Reach level 10 with any class
Freeze an enemy
Hold 5.000 Clefines in your inventory
Complete 50% of all sidequests
Complete the prologue
Retrieve the Bagpipes
Revive a party member
Complete a sidequest
Play with 2-4 players
Buy all skills from all classes
Upgrade all skills from all classes to level 3
Collect all shop books
Burn an enemy
Hold 25.000 Clefines in your inventory