Here is the full list of all 47 Operencia: The Stolen Sun achievements.
Complete the game with any difficulty settings
Complete the game with at least two difficulty settings switched to hard
Buy everything from Elia's stock
Fully reveal all maps
Reveal all secrets
Open all locked chests
Dig up all buried treasures
Reach the highest level with all characters
Find "Letter to Olek" in Gate to the Underworld
Brew all potions
Find all recipes
Reveal the secret chest in Bálványos' block room
Defeat all enemies in the game
Place both skulls onto the coffin in the First Royal Tomb
Discover all campfires
Unlock everything on two talent trees for at least one character
Try to remove the channeling crystal after it was activated in the Glass Palace
Complete Gate to the Underworld
Complete the Second Royal Tomb
Levitate twice in the Second Royal Tomb
Reach 220+ on all three main battle stat at the same time
Get the secret treasure of the Hungry Plant in The Great Forest
Equip a full armor set on any character
Defeat an enemy group with one hit
Complete Deep in the Copper Forest
Get the treasure from the well in the Copper Forest
Complete Copper Forest
Unlock and use the Copper Forest's workshop door from the inside
Complete Atop the World Tree
Use up all the cheap wine in Atop the World Tree
Complete World Tree
Force all mouths to close at least once in World Tree
Complete Bálványos
Complete Deva Fortress
Open the skeleton's tresure chest in Deva Fortress
Buy any equipment from Elia
Pile up ten pieces of Firewood
Complete The Great Forest
Complete the First Royal Tomb
Unlock the last tier of at least one talent tree
Complete Lake of Anna
Unlock at least three skills from any talent tree
Spend two minutes under water in Lake of Anna
Equip an item to all slots of a character
Level up a character
Win a battle