Here is the full list of all 28 Eventide 3: Legacy of Legends achievements. It takes around 5-6 hours to unlock all of the achievements on Windows.
Finish both Portal Travel Minigames without a mistake
Find all the ornaments
Finish any Hidden Object Puzzle in less than 30 seconds
Stop the ritual and defeat the King
Finish all Minigames without skipping
Help John acknowledge his powers
Find all the cards from the Pantheon
Complete all Hidden Object Puzzles without using a Hint
Read all the notes placed throughout the game
Bring the Zmey Scepter
Find half of the cards from the Pantheon
Prove yourself and summon Perun
Find out about the King's evil plan
Complete 3 Hidden Object Puzzles with no more than 5 mistakes in each one
Find half of all ornaments
Get out of the dungeons
Free and heal the Cloudman
Watch all the cutscenes from the first hour of the game
Find the Prism
Finish a Minigame in less than 1 minute
Finish three Minigames in a row without skipping
Get to Vyrai
Uncover and heal Aitvar
Complete any Hidden Object Puzzle without using a Hint
Find 3 Hidden Objects in 3 seconds
Find the first card from the Pantheon
Find the first ornament
Finish all Battle Runes Minigames without a mistake