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.
Play with all characters in game.
Play with all classes in game.
Choose a weird combination of character and class.
Clear 50 dungeons.
Continue the game after a game over.
Visit your Kitchen inside the game.
Complete a campaign using all 5 Game Developers as characters.
Finished the campaign.
Visit every single place in game.
Buy the highest weapon upgrade available.
Buy all goodies in game.
Kill a dragon.
Buy the highest armor upgrade available.
Clear 10 dungeons.
Unlock the Necromancer class.
Unlock the Shaman class.
Reach Level 30 in every character of your group.
Reach Level 30 in a trio.
Spend 9.001 golds.
Unlock the Knight class.
Earn 9.001 golds.
Unlock all masters.
Unlock a new master.
Use a potion while full health.
Unlock the Barbarian class.
Unlock the Bard class.
Clear a dungeon.
Reach Level 15 in a specific Spell.
Win a battle with 7 monsters.
Unlock the Game Developers that made the game.
Reach Level 5 in any character.
Gather 10 grindstones from veins.
Unlock the Hunter class.
Roll 1 in any random roll.
Make the blacksmith dance.
Roll 20 in any random roll.
Kill an elite minion.
Gather a grindstone by mining veins.
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!
Reach Level 15 in any character.
Reach Level 30 in any character.
Finish the storyline as fast as you can (less than 365 days but you may extend that to 465).