The Planetary Defence System, introduced in Jak 3, is found in the center of the Catacombs, and it said to be the only hope to defend the planet from the threat of the Dark Makers. It consists of a large Oracle-like statue (which was revealed to be the control system for the Precursors) and two devices that each fire an Eco beam - one of Dark Eco and one of Light Eco. These beams are fired at angle; where they meet, a new, more powerful beam is emitted. It is powered by a sphere containing 4 light eco crstals and 4 dark eco crystals which have been collected over most of the game.
Role
The Planetary Defence System is first mentioned by Count Veger some time after Jak has returned to Haven City. He mentions that the Precursor Monks have given him the knowledge to activate the system, though he will only activate it if begged to do so.
When Jak looks through the Astro-Viewer the first time, the Precursors say that the Planetary Defence System is the only hope for defeating the Dark Maker threat.
The system is finally activated near the end of the game, though Cyber-Errol escapes in a Terraformer.
Notes
While the single beam from this weapon passes straight through the Dark Maker ship, the Precursors inform Jak that it would be ineffective if the ships shields were raised, highlighting how close Precursor and Dark Maker technology are.