Considering that in one mission we have to destroy a Hacking Device that is operated by the Mantis this may explain how they managed it to use them on earth. The thing is that those Ancient relays seem to make it possible to controll Ancients in other systems (maybe just planets) if we consider that the last mission at EiU was to destroy the Relay that seems to controll this whole operation with Calon as it´s origin.
Also in the Mission "Distant relatives" we find out that in each system on a planet such a relay is placed (that they can only be seen during the mission is another thing) but here Ancients land when we approach the relay in order to defend it so it would confirm that the Ancients could have been operated on other Systems as well.
This is something even
@Poland is confused about (and me as well) cus even when i watch the trailer for TC4 over and over again i can not find any point where a Giza can be seen buried at the planet. Aside from that there is till the Artifact that seems to have no more relvance to the original story after we have collected all pieces. If my memory serves correctly the only reason why we have collected the Artifact was to "open the Wormhole" in order to travel to Sirius while the map that can bee seen at the Artifact can nowhere be found.
Even if we would take the trailer again it would only have 2 Planets where one is the Mantis Homeworld while the other is a destroyed one with an RDX hangar for the Reactor Challenge. This would still mean that 2 planets are missing as the rings at the artifact indicate at least 4 Plantes should be present in the system it shows + my theory of a planet and a moon who are hidden "inside of the sun".
the most issue with the ancients on earth in unrest was that the mantis had power over the earth relay. meanwhile in "dark premonition" the secret methanoid pilots are attacking us on our way to carl sagan and in the back route ancients attacks us for the reason because the relay is still hijacked by the mantis. the reason why the methanoids playing two-games here is they don't want us to know the truth.
later on calon it was necessary to lease the dots and connection from the mantis and pirates. the entity said if he didnt compensated himself on calon he could die, he keept himself alive. look what happened on aurora and desai.
the ambassador said we shouldnt go deeper in the dark side of the ancient past and maybe this would tell us what the valatory sect actually is. but most of the valatory sect are theories because there is not alot to tell, but let me tell you something else. most of the anti matter techs are listed in on the old ancient archvies, even before tay ceti, sirius and draconis the ancient storyline began slowy in sol system.
as mysterious the brotherhood is we know more about them than the valatory sect.
tau ceti is splitted in 4 part story stelling
part 1 - we need to search for the ancients as the mantis story continues and pirates story gets bigger with more ancient activities on venar.
part 2 - invaded earth with ancients and mantis. they seem like an ally and we need to release them and destroy the relay station, later on we will know that other sol planets are invaded as well.
part 3 - is the mysterious part. finally we can confront the origin of the ancients and they seem more advanced as we usual knew in sirius. its about trust and failure in the past. the methanoids warn us to join the ancients, but we cant join them without a trust. planck did die on calon, but the entity compensate him as well he did it before. in the end the entity will show his trust to us and wants to guide us for the first attack on the mantis planet. the ancients are free, but few more dots are left on the mantis planet.
part 4 - i think this part will show us the dark side of the ancients a little bit and mostly they want refuse to help us. its not about to kill the queen, its about to release the ancients finally and this kinda situation will be interesting for the future storyline.