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