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