The “Planetary Shield” artifacts allow you instantly increase your celestial bodies defense by large amounts.
Each rarity of “Planetary Shield” will increase your celestial bodies defense, and temporarily reduce your range & speed by:
Common: +50% Defense / -80% Range & Speed; Rare: +100% Defense / -80% Range & Speed; Epic: +200% Defense/ -80% Range & Speed; Legendary: +350% Defense / -80% Range & Speed; Mythic: +550% Defense/ -80% Range & Speed.
Some important things to note, are that once you have activated a “Planetary Shield”, all moves you make from the celestial body will move at a massively reduced speed & cannot reach very far across the universe. Once the threat is over, you can then deactivate the Planetary Shield to restore the celestial body back to its initial Defense, Range & Speed stats, however the Planetary Shield artifact will disappear, as they are only single use.
This planet has a “Planetary Shield” on it. Any attacks sent here will do little damage, but rest assured, the reduced Range & Speed mean that it wont be a threat to you, as long as the Planetary Shield is still active. This one also looks a little different because it doesn’t have a biome - it is “Ancient”.
In the Early game, “Planetary Shields” are not particularly valuable. Fighting between small planets generally means that you should be able to reconquer any nearby celestial bodies you use, and having an active Planetary Shield means that your expansion will be nerfed. The bonus defense provided by the Common/Rare artifacts you will find is rather low, so they tend to be better kept for later in the game, so you can “waste” them when defending larger celestial bodies.
In the Mid-Late game, “Planetary Shields” become far more powerful, since you will likely come into possession of several which are of Epic (or higher, if you’re lucky) rarity. They must then be used more sparingly, such as in situations where you have multiple enemy attacks set to hit one of the important planets within your empire.
Another tactic in the late game can be to send a large attack with a Photoid Cannon that also sends a Planetary Shield (similar to the strategy with Black Domains), which you can then use to defend the newly conquered planet until you are able to fill it with energy/take over other nearby planets. This strategy is best if you are wanting to do significant damage to an opponent, though can be tough to execute.
The stats provided by a rare Planetary Shield. A large increase to Defense, but a reduction in Speed & Range.
As you can see, these artifacts give massive bonuses to defense, but at the cost of rendering your celestial body useless for any offensive purposes, including expansion, due to the reduced Speed & Range.
Take note of the description, where it states that, when deactivated, the artifact will be destroyed.