Here is the full list of all 20 Mystika 4 : Dark Omens achievements.
Finish the game with Tenebria !
Finish a level in less than 30 seconds
Reach the high score (7 steps)
Finish the game with Alrik !
Defeat Selenia !
Sell the artifacts you found (7 steps)
Trigger as many traps as possible (7 steps)
Help to restore the world (7 steps)
Explode as many rocks as you can (7 steps)
Break as many chains as you can (7 steps)
Dig to find more coins (7 steps)
Become rich! (7 steps)
Get the stars ! (7 steps)
Defeat Sarel !
Cast as many spell as you can (7 steps)
Reach the middle of the map
Defeat Golem !
Defeat Elf !
Complete the first 'Spot the difference'
Find the first artifact