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