Here is the full list of all 21 Before the Echo achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Defeat the Holiday Whompa.
Successfully defeat your first enemy.
Complete a battle without failing a spell.
Discover the name of she who controls fate.
Get her back.
Beat the game on any difficulty.
Synthesize Iridium.
See the hidden ending.
Learn all spells.
Defeat an enemy using only poison spells.
Defeat an enemy on the seventh floor using only Arclight.
Successfully complete a synthesis at 25% odds of success or lower.
Defeat an enemy with less than one second remaining on the clock.
Defeat an enemy within eleven seconds.
Recover over 150 mana in a single battle, and win.
Obtain every droppable item in the game at least once.
Obtain all three droppable items from any single enemy.
Trigger Boost a Trigger Boost.
Queue up five spells in a row.
While learning a spell, achieve 100% accuracy for the entire song.
Synthesize every recipe in the game.