Here is the full list of all 26 Vidar achievements.
Get help from three people in town identifying a recovered amulet
Get an Imp Oil Lantern
Groa and Csaba Separate
Dig a Tunnel Through the Dark Cave
Witness a Fight Between Mihaly and Bernadett
Recover Borbalo's Liquor
Get Help Identifying Monster Bones
Have Tamas Bake You Some Bread
Reach the Ruins With 8 Villagers Alive
Reach the Ruins With 12 Villagers Alive
Drink Expensive Wine With Dani and Cecilia
Help Katarina Become the Blacksmith
Get Etel Outside Patrolling Vidar
Anger both Piri and Bernadett in the same game
Go hunting with Cail
Watch a fight between Csaba and Borbalo about religious traditions
Use a smoke bomb in the final confrontation
Rescue Robert and Cecilia from the fire
Help Robert find his professional calling
Eat every mushroom
Get at least 10 people to attend Dani's wake
Say goodbye to Sandor in the spirit realm
Save Katarina from a poisonous spider bite
Help Dorottya stabilize the cave
Help Szabina complete her investigation
Unlock all of Mihaly's songs