>>16082039The dex entries mention a few things over and over: It has strong legs, a powerful bite, and intimidates it's enemies. It's intimidating nature is mentioned in less than half of the entries. By this logic, everything with Intimidate should be Dark type.
Compare this to some other Dark types. Umbreon's glowing rings strike fear into the hearts of those near by. Houndoom's entries describe 'eerie' howls and neverending pain. Or how about this little gem from Murkrow: "Feared and loathed by many, it is believed to bring misfortune to all those who see it at night. "
Being feral has nothing to do with Dark type. All wild pokemon are feral by definition.
