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 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
Upgrade all the unique weapons in new game+
Defeat the Super Sheep 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!
Level your Librarian up to LVL 60
Beat the game in new game+ without any generic recruits
Defeat the Super Sheep in the standard game
Earn all the unique weapons in the standard game
Earn all the unique armor in the standard game
Earn all the books from bonus challenges in the standard game
Reach wave 100 on Endless Challenge 2 in the standard game
Complete the game in new game+
Beat all side quests in new game+
Level your Librarian up to LVL 40
Level your Librarian up to LVL 25
Beat any level on Extreme.
Complete the standard game
Beat the standard game without any generic recruits
Unlock a level 20 skill
Unlock all 6 character classes (not counting Librarian)
In battle, boost a character to the max boost level
Level your Librarian up to LVL 10
Use an advanced targeting option
Visit the accessibility menu (options->accessibility)
Visit the controls menu (options->controls)
Visit the tips menu (overworld->tips)