Here is the full list of all 18 Celestian Tales: Old North achievements.
Defeated the Grey Giant.
Completed the game once with Aria as main character.
Completed the game once.
Collected all Backers Honour Medals.
Upgraded all Bow weapons to the highest level.
Upgraded all Spear weapons to the highest level.
Upgraded all Dagger weapons to the highest level.
Upgraded all Crossbow weapons to the highest level.
Upgraded all Sword weapons to the highest level.
Reached party level 30.
Owned more than 9999 Livre.
Upgraded all Axe weapons to the highest level.
Completed the game once with Cammile as main character.
Completed the game once with Isaac as main character.
Completed the game once with Lucienne as main character.
Completed the game once with Reynard as main character.
Completed the game once with Ylianne as main character.
Completed the game with each main character at least once