Retros are a fanatically hostile faction. They say they hate technology, that's why they fly around in space ships and shoot at you with lasers.
Luckily they usually fly weak Talons like the Pirates, except sometimes in guild missions asking to destroy a Retro Nexus or Pegasus . Their ships are marked purple if you have a B&S radar. They never control systems, but you can meet them from time to time in uncontrolled systems or in missions.