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