Here is the full list of all 30 Defender's Quest: Valley of the Forgotten achievements.
Visit the tips menu (overworld->tips)
Level your Librarian up to LVL 10
Level your Librarian up to LVL 25
Level your Librarian up to LVL 40
Level your Librarian up to LVL 60
Unlock all 6 character classes (not counting Librarian)
Earn 201 Blue Stars
Earn 201 Gold Stars
Earn all the unique weapons in the standard game
Earn all the unique armor in the standard game
Upgrade all the unique weapons in new game+
Upgrade all the unique armor in new game+
Earn all the books from bonus challenges in the standard game
Earn all the books from bonus challenges in new game+
Reach wave 100 on Endless Challenge 2 in the standard game
Beat any level on Extreme.
Complete the standard game
Complete the game in new game+
Defeat the Super Sheep in the standard game
Defeat the Super Sheep in new game+
Beat all side quests in new game+
Unlock a level 20 skill
In battle, boost a character to the max boost level
Visit the accessibility menu (options->accessibility)
Visit the controls menu (options->controls)
Beat the standard game without any generic recruits
Beat the game in new game+ without any generic recruits
Earn 180 gold stars without any generic recruits. For your sanity, we recommend increasing XP gains to 300% in the options menu!
Reach wave 100 on Endless Challenge 2 in new game+
Use an advanced targeting option