Here is the full list of all 28 AereA achievements worth 1,000 gamerscore. It takes around 20-25 hours to unlock all of the achievements on Xbox One.
Upgrade all skills from all classes to level 3
Buy all skills from all classes
Use a skill 100 times or more
Collect all shop books
Retrieve the Baton
Hold 25.000 Clefines in your inventory
Retrieve the Drum
Retrieve the Violin
Reach level 50 with any class
Retrieve the Bell
Complete all sidequests
Reach level 30 with any class
Retrieve the Sousaphone
Hold 10.000 Clefines in your inventory
Retrieve the Accordion
Retrieve the Harp
Complete 50% of all sidequests
Retrieve the Lyre
Hold 5.000 Clefines in your inventory
Reach level 10 with any class
Poison an enemy
Burn an enemy
Freeze an enemy
Retrieve the Bagpipes
Complete the prologue
Revive a party member
Play with 2-4 players
Complete a sidequest