Here is the full list of all 20 Mana Spark achievements.
Have 4 pets at the same time
Kill the second boss
Kill 2 or more enemies with the same attack
Complete a sacrifice
Activate the same Peculiar Room button 3 times in a row.
Leave a Wolfsbane Wood level with all the boars alive
Kill the first boss
Survive the Wolfsbane Woods while taking zero damage
Beat the game
Beat the game with each playable character
Survive a room with 15 or more spiders
Kill all the enemies in a room without attacking once
Survive the Buried Tunnels while taking zero damage
Survive the Aberrations Chambers while taking zero damage
Read all the available bookshelf texts.
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