Here is the full list of all 42 Knights of Pen and Paper +1 achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Finished the campaign.
Kill a dragon.
We know it may be frustrating to die so we've just rewarded you with this achievement. Do not give up, the game is about to begin!
Visit every single place in game.
Unlock a new master.
Reach Level 30 in any character.
Reach Level 30 in every character of your group.
Unlock the Necromancer class.
Buy the highest weapon upgrade available.
Unlock the Shaman class.
Reach Level 30 in a trio.
Use a potion while full health.
Buy the highest armor upgrade available.
Spend 9.001 golds.
Earn 9.001 golds.
Unlock the Barbarian class.
Unlock the Knight class.
Clear a dungeon.
Reach Level 15 in a specific Spell.
Continue the game after a game over.
Gather 10 grindstones from veins.
Reach Level 15 in any character.
Unlock the Bard class.
Unlock the Hunter class.
Unlock the Game Developers that made the game.
Gather a grindstone by mining veins.
Make the blacksmith dance.
Roll 20 in any random roll.
Win a battle with 7 monsters.
Roll 1 in any random roll.
Reach Level 5 in any character.
Kill an elite minion.
Choose a weird combination of character and class.
Complete a campaign using all 5 Game Developers as characters.
Play with all classes in game.
Play with all characters in game.
Visit your Kitchen inside the game.
Unlock all masters.
Finish the storyline as fast as you can (less than 365 days but you may extend that to 465).
Buy all goodies in game.
Clear 10 dungeons.
Clear 50 dungeons.