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