Here is the full list of all 24 Secrets of Magic 2: Witches and Wizards achievements.
Collect at least 78 crystals of any kind
Finish all the levels in Challenge mode
Get 300 stars
Destroy at least 28 spiders
Destroy at least 50 big rocks
Destroy at least 380 stones
Get 200 stars
Upgrade twice the Stake power-up
Upgrade twice the Wand power-up
Upgrade twice the Hammer power-up
Play 50 levels
Destroy at least 280 spider webs
Upgrade twice the Whirlwind power-up
Destroy at least 650 wooden gates
Destroy at least 120 imps
Upgrade twice the Lightning power-up
Play 20 levels in a row
Upgrade twice the Torch power-up
Upgrade any power-up for the first time
Explode at least 30 bombs - bonus power-up
Finish the first 10 levels with 3 stars in each level
Make a combo of 25x or higher
Make a combo of 20x
Make a combo of 15x