Maybe building their own colony elsewhere on the map and just interfering with all your possibiities for expansion? Lurk around all the exposed mineral deposits?
How about an event where the raiders try to find some exposed power conduit, and hook something into it that drains a lot of power, with the idea being they will cause your turrets etc to shut down.
How about an event where the raiders try to find some exposed power conduit, and hook something into it that drains a lot of power, with the idea being they will cause your turrets etc to shut down.


