Edit: Apparently, killing the Darkness with the magic missile doesn't give you the achievement. You have to kill it with other items. --- Yet, the Arcana is the means by which all is revealed. Beyond the beaten path lies the absolute end. It matters not who you are...Death awaits you.
Ah cool. Me and my friends were trying to figure that out. Strange way of getting a chest, but I'm not a fan of needed a specific item to do it : / --- You guys can have your shorter kill times with your fancy sharp swords and bludgeoning weapons. I'll spend the extra 5 minutes looking awesome. - Typhlax