I got tired of having Mogrul's thugs try mugging me whenever I was out of sight of guards in Raven Rock, so I killed him. And his little dog--er constant companion. No problem.

Until I went back to Fort Dawnguard, only to run into Mogrul.

As it turns out, there are http://www.uesp.net/wiki/Dragonborn:Mogrul of http://www.uesp.net/wiki/Skyrim:Mogrul. And they're almost identical.

Maybe orcs have taken to cloning.....

Its a recipe for WAR!