The “Monolith” artifacts give a bonus to one or more of the base stats of the celestial body which it is active on. The bonuses vary, dependent on the biome that the artifact originated from, but will always give a bonus to both the Energy Capacity & Energy Generation stats. This bonus scales from 5% for a Common artifact, up to 15% for a Mythic artifact (or even more, depending on the biome!).
There is nothing unintuitive about the “Monolith”, or any of the other stat-boosting artifacts - they can be activated and deactivated as many times as you wish, can be used on any level of celestial body, and will provide their bonus instantly (once the blockchain transaction is confirmed).
This planet has a “Monolith” on it. Watch out for high energy attacks coming from here - and be wary that you will have to send larger attacks to deplete its energy reserves before you can conquer it!
In the Early game, “Monoliths” pair incredibly well with celestial bodies that have x2 Energy Generation Moons. Any extra bits of energy will help to increase your expansion rate and help to start dominating within your region of the universe. They might also help to give you an edge over any nearby players whom try to attack you, allowing your celestial bodies to keep themselves topped up with energy quicker.
In the Mid-Late game, “Monoliths” are great additions to have on your “feeder” planets - planets which you are using to fill up the energy of your larger, more powerful celestial bodies. Having boosted energy regeneration will allow you to play more freely, attacking more/larger celestial bodies, continued expansion and also the safety of having an empire which always has energy ready for defensive purposes.
The stats provided by a rare Swamp Monolith - a well-rounded artifact over all, with 10% buffs to every stat except defense.
As you can see, this artifact gives a bonus 10% to both Energy Capacity & Energy Regeneration from the Monolith, along with a 10% also to Range & Speed - courtesy of the Swamp biome which this artifact originated from.