I found this out the other day, the devs have introduced a new storyline into SW where a bunch of lvl60 undead guys try to take over the city and some other towns too.
Now the bug is, very simply, the guards will keep agro, the undead guys don't actually ever die, and you can just keep hitting them for at least 30mins until they despawn. This is very handy for increasing your weapon skills, it took me only a few minutes to max out polearms, unarmed, and all my other skills.