A Planetary ring is billions and billions of satellites armed with photon cannons. Any planet with Planetary rings are a threat to anyone's ship as they are almost impossible to break them on their own. Just running through them will cause an massive amount of damage. Its guaranteed that any world that is to join the United Star Corps must have planetary rings as they are the best protection from the Syn. They were designed and invented to counter the Syn as well as pirate factions, many pirates won't attack any world that these as they have loss too much. Usage of these structures is an massive ordeal costing nearly 2.8 trillion credits per layer is relatively cheap but requires perfect aim, being off by one degree will cause a hole in the Planetary ring causing a major threat to the defensive structure. It must be perfect or the ring is ineffective.