Here is the full list of all 44 Mages Initiation: Reign of the Elements achievements.
Acquire one of each drink type at the tavern.
Kill 50 enemies.
Beat both Mage sparring partners.
Win a hand of Demon's Deal.
Earn your first spells from the Sphere of Knowledge.
Win the maximum number of Demon's Deal rounds.
Pick all mushroom clusters in the forest.
Spare a tainted life.
Complete the first trial.
Earn your second spells from the Sphere of Knowledge.
Ele'port to each pillar stone location.
Optimally complete the Fire side quest.
Optimally complete the Water side quest.
Optimally complete the Earth side quest.
Optimally complete the Air side quest.
Complete all class-based side quests with optimal outcomes.
Return a borrowed item.
No sacred avian was harmed.
Complete the second trial.
Earn your third spells from the Sphere of Knowledge.
Complete the severed circle story branch.
Kill one of each monster type.
Find and read all books and notes.
Find all three "Tear" class brooches.
Extinguish the Redcaps' camp fire.
Reject a dark deal.
Make a red delivery to the Greencaps.
Complete the third trial.
An ally survives.
Both allies survive.
Defeat the Big Bad.
Max out all your stats.
Finish the game with max XP / score.
Complete the game.
Finish the game with all 4 classes.
Kill only the bosses (no regular monsters).
Earn all Fire class Bonus points.
Earn all Water class Bonus points.
Earn all Earth class Bonus points.
Earn all Air class Bonus points.
Kill 100 enemies.
Kill 500 enemies.
Kill 1,000 enemies.
Beat the game without equipping any extra gems or items (after the initial tutorial).