Here is the full list of all 36 Secrets of Magic: The Book of Spells achievements.
Complete the Venom Antidote Spell
Finish all the levels in Challenge mode
Get 300 stars
Complete the Spell of Awakening
Complete the Spell to Remove a Werewolf’s Curse
Use the Torch power-up on at least 25 spiders
Collect 500 spell ingredients
Complete the Spell to Hear Secret Thoughts
Get 200 stars
Complete the Spell of Invisibility
Upgrade twice the Lightning power-up
Complete the Spell of Truth
Destroy at least 600 wooden gates
Upgrade twice the Stake power-up
Play 50 levels
Complete the Spell of Healing
Upgrade twice the Whirlwind power-up
Upgrade twice the Wand power-up
Complete the Spell to Fly a Broom
Destroy at least 130 stones
Complete the Spell of Time
Upgrade twice the Hammer power-up
Destroy at least 245 spider webs
Complete the Spell for Invoking the Power of Lightning
Upgrade twice the Torch power-up
Complete the Spell of Strength
Make a combo of 25x or higher
Complete the Spell for Invoking the Power of Wind
Destroy at least 100 imps
Complete the Spell to Imprison an Evil Spirit
Finish the first 10 levels with 3 stars in each level
Upgrade any power-up for the first time
Make a combo of 20x
Complete the Spell for Invoking the Power of Fire
Complete the Spell of Protection
Make a combo of 15x