Here is the full list of all 51 The Book of Unwritten Tales 2 achievements. It takes around 25-30 hours to unlock all of the achievements on Windows.
Get seriously lost in the Darkwood
Win the Nim game without cheating
Hit all the symbols in the Drunken Punch minigame
Finish the cleaning tasks of the headmaster
Prevail against evil
Watch the entire end credits
Return unscathed from the castle
Turn Timmy back to normal
Invoke the arch mage
Beat the Fear
Chase off the spider in the Darkwood
Obtain the ghost detecting device
Win the battle, but not the war
Obtain the Red Pirate's compass
Obtain the Book of the Dead
Obtain the Spark of Life
Free your team mates
Fulfill the oracle's wishes
Find Rémi and learn more about Wilburs staff
Free your leader and your noble steed
Issue all four laws
Solve the tasks of all four gods
Illuminate the dark cave
Rescue Ivo
Help the zombies with the slate production
Bring back a friend
Disguise convincingly
Strengthen a friendship
Restore the electricity
Escape despite the surprising twist
Animate your golem
Mix the magic ink
Build your own golem
Ask the right math problem at the first go
Receive the key to the city gate
Steal the lamp and flee
Get Nate sobered up
Master your first day of school
Solve the time travel side-quest
Make the library reappear
Free the school of kobolds
Read all student files
Escape the Elfburrow
Receive the hat of the Master Fisher
Be enlightened five times
Find out that Ivo is pregnant
Finish the tutorial
Survive the fall