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