Occasionally, you’ll stumble upon safes and lockboxes that require a specific key. Keys will either be found lying around or on the person of a named zombie. Interact with the locked receptacle, and it’ll tell you the name of the key, which should serve as a bit of a clue. Find the key location or the named zombie who possesses it, then open the box. Crack open ten of these to unlock the achievement.

If you need help for where the Lockboxes or where there keys are, check out our Dead Island 2 all Lockboxes and Keys Locations Guide.