Invaders... is an inaccurate word, since the Sesh Empire owned these parts about a million years ago. Of course, they are all dead now, but unfortunately, their Remnant War Clones never got the memo. There are too many automated factories making ships and clones out there in the galaxy to get rid of them all. Lucky their starships never venture into inner system, they send patrols regularly and they attack mindlessly on sight.
The two most common variants we encounter are the Gaeru Barth and the Gaeru Zalg. They are built to last, simple to manufacture, and brute force their way through the battlefield.
The real nasty is the Gaeru Zalg. They handle even worse than the Barth's in an atmosphere, but they have an oversized energy cannon. Fortunately, they have to charge up to be used, but it's a one hit, one kill sort of weapon, and they can do serious damage even to capital vessels. Unfortunately, they still have half the missiles of a Barth on top of that.