If you actually read the trilogy I mentioned, by "elimination" the author doesn't mean an invasion. The advanced races literally manipulates laws of physics to

If you actually read the trilogy I mentioned, by "elimination" the author doesn't mean an invasion. The advanced races literally manipulates laws of physics to its extreme to remotely wipe out star systems without ever exposing themselves. The methods range from rudimentary ones like turning the star of a system nova to god like ones like dropping the dimension level of a region of space from 3D to 2D. Yes, it's a fantastic series of reading :)