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