Pick up 50 enemy drops.
Enemies will drop loot for you to pick up after battle. Not every fallen enemy will drop something but most will. Pick up a total of 50 on 1 save file to get the achievement. If you die between saves or auto-saves the progress will be lost. Luckily you should get an auto-save frequently should you forget to manually save your progress.
You should be able to get this early on in act 1 after visiting the town of Valvenor.