Here is the full list of all 10 Monsters and Weapons achievements.
Win the game with every class.
Have your inventory completely filled with spellbooks during a run.
Defeat the final boss with more health than you started the fight with.
Defeat 100 monsters in a single run.
Die to the butterfly.
Win the game 10 times with a class.
Reach level 10 during a run.
Reach 300 health during a run.
Win two times in a row, using two different classes.
Win the game in legendary mode.