Just to shine a little bit of light on everyone's random guesses (some were really close), the correct place to kill shades is *drumroll* Mort'ton. I think you need to be midway through or finished "Nature Spirit" quest to get there. Once you're there, you can battle Loar (?) shades, Phrin (?) shades , etc. and the lowest shade is level 40 so 78 should be no problem. Just remember to run through the swamp as the ghasts will rot your food and the swamp might too. If you do the "Shades of Mort'ton" quest however, you might be able to use the general store to sell food to and buy from. Good luck killing those 78, you'll need it!
