Here is the full list of all 20 Mana Spark achievements.
Leave a Wolfsbane Wood level with all the boars alive
Kill the first boss
Kill the second boss
Beat the game
Beat the game with each playable character
Complete a sacrifice
Survive a room with 15 or more spiders
Kill 2 or more enemies with the same attack
Kill all the enemies in a room without attacking once
Survive the Wolfsbane Woods while taking zero damage
Survive the Buried Tunnels while taking zero damage
Survive the Aberrations Chambers while taking zero damage
Read all the available bookshelf texts.
Activate the same Peculiar Room button 3 times in a row.
Use the freezing bomb to freeze yourself AND an enemy at the same time
Unlock and upgrade everything available at the encampment
Finish the game after eating a Spicy Burrito.
Kill the third boss
Survive the Forgotten Crypts while taking zero damage
Have 4 pets at the same time