Here is the full list of all 15 Heroes of Loot achievements.
Slay 5000 monsters
Drink from the well
Activate a statue
Unlocked Barbarian character
Kill a minotaur
Maximise dungeon difficulty
Become level 10
Reach dungeon level 15
Get the "Lens of secret"
Become invisible
Play in the Arena room
Kill a cyclops
Save a lost soul
Buy a titanium shield
Upgrade the difficulty of the dungeon