Here is the full list of all 100 Spellbook Demonslayers achievements.
Level up Meltdown to level 10.
Survive 20 minutes with 22 or more Malice.
Survive 20 minutes with 33 or more Malice.
Survive 20 minutes with 44 or more Malice.
Survive 20 minutes with 55 or more Malice.
Survive 20 minutes with 66 or more Malice.
Survive 20 minutes with 77 Malice.
Reach level 80 with any Spellbook.
Level up Shrine Maiden to level 4.
Level up Acrobatics to level 4.
Reach level 50 with Vella.
Survive 20 minutes with 13 or more Malice.
Level up Demon Feast to level 4.
Level up Samsara to level 4.
Level up Cataclysm Sigil to level 10.
Level up Revengeance to level 4.
Reach level 60 with any Spellbook.
Reach level 50 with Wolfe.
Obtain 10 buffs at once.
Survive 20 minutes with 7 or more Malice.
Level up Indra's Sigil to level 10.
Gamble at Ibrahim's Emporium 4 times in a single run.
Level up Lethality to level 4.
Reach level 50 with Tammy.
Level up Overload to level 10.
Level up Juggernaut to level 4.
Level up Thickening to level 4.
Level up Toxic Blizzard to level 10.
Level up Fortification to level 4.
Open 69 treasure chests.
Successfully complete any stage with 4 copies of the same spell at level 10.
Unlock Enigma
Level up Airavata's Arrival to level 10.
Level up Reverberation to level 4.
Level up Brainpower to level 4.
Play 3 runs.
Activate a Revive.
Level up Slipstream to level 4.
Level up Inferno to level 10.
Level up Timmy & Tommy to level 10.
Level up Blood Barrage to level 10.
Level up Intensity to level 4.
Reach level 50 with Speare.
Level up Mending to level 4.
Level up Monsoon to level 10.
Have 4 level 10 Spells at once.
Level up Star Scourge to level 10.
Level up Brutality to level 4.
Level up Spectre Shot to level 10.
Earn 13 or more Astral Flowers in a single run.
Achieve a Regeneration amount of 77 or higher.
Survive for 4 minutes.
Reach level 40 with any Spellbook.
Level up Clairvoyance to level 4.
Obtain 5 buffs at once.
Level up Deadly Aim to level 4.
Survive for 13 minutes to begin the Slaughter.
Reach level 20 with any Spellbook.
Reach level 125 with 77 Malice.
Reach level 125 with 77 Malice with every spellbook.
Reach level 100 with any Spellbook.
Reach level 125 with any Spellbook.
Reach level 50 with Jeanne.
Reach level 50 with Astrid.
Reach level 50 with Berry.
Reach level 50 with Sly.
Reach level 50 with Eden.
Reach level 50 with Enigma.
Obtain 20 buffs at once.
Obtain 30 buffs at once.
Obtain 40 buffs at once.
Obtain 50 buffs at once.
Level up Nightshade to level 4.
Level up Shotgun to level 4.
Level up Skewer to level 4.
Level up Fracture to level 4.
Level up Trailblazer to level 4.
Level up Cremation to level 4.
Level up Dark Moon to level 4.
Level up Synthesis to level 4.
Level up Bloodletting to level 4.
Level up Deathbound to level 4.
Level up Thunderswarm to level 10.
Level up Freezing Rain to level 10.
Level up Blitzkrieg to level 10.
Level up Madame Death to level 10.
Level up Fire of Sinai to level 10.
Level up Ardor to level 10.
Level up Frost Shear to level 10.
Level up Acid Breath to level 10.
Level up Eyepopper to level 10.
Level up this spell to level 10.
Level up Flame Lance to level 10.
Level up Throne of Darkness to level 10.
Level up Bloodspark to level 10.
Level up Shrinkage to level 10.
Level up Agni's Sigil to level 10.
Level up Midnight Sigil to level 10.
Achieve a movement speed of 420% or higher.
Level up Winter Sigil to level 10.