Location: Everywhere so it seems
Threat Assessment: 4. They are certainly better than storm troopers. Armored creatures armed with one shot energy weapon/swords. Despite high tech/magic(?) they still ride horses. Kill one and the head breaks open and a worm thing burrows into the ground. Does that mean it can be reborn? I don't know.
Limitation: About as smart as you want your grunts. Not fast.