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