SirNoods

I am trying to complete the Special Delivery achievement but I have no clue which enemies to defeat or how to go about effectively completing it. I can't see to find a strategy, map or method of doing this. I have been playing for days now and I can't get the % to move on the achievement. Can someone give me direction as to how I can effectively complete this achievement? Can you please advise me as to what mobs I need to fight or what maps help get this done?