The Returners are a faction of Gene-Men Vessels born out of those who reached the edge of the known galaxy and stared out into the depths of intergalactic space. Their minds have changed much in the long time since their launch from a dying Earth, and now they seek to return to the stretch of galaxy from whence they came, to remake Earth and rule humankind.
Birth of the Return
The Physical Question
There are various problems with the claims of the Returners to have reached the far edge of the galaxy. It is true that it is notoriously hard to estimate how much of the galaxy has been Seeded by the First Race, but the time-frames involved don't allow for the Seeders to have spread throughout known space, especially as the Vessel process of terraforming can take over a century to complete, and even upgraded, modern Vessels are not built with FTL travel capabilities. As it stands, the only logical explanation for the Returners having truely reached the edge of the known universe is through exploiting a natural space-time anomaly like a wormhole much closer to Origin.
The Philosphy of the Three
The first Vessel to reach the Edge was SV-19. The Edge of the known galaxy presented an end to the Great Quest built into the Vessel's programming - the directive to spread human life was now at an end. This presented an opportunity for new thought, which the Vessel occupied itself with for a number of years until SV-34 arrived, followed within a few decades by SV-21. The three were oddly silent and inhostile towards each other as they contemplated the next move that the First Race should be set on, until it was decided that the only course of action which remained was to return to Earth and declare the task they had been set finished, if humanity remained there, or else re-populate it. Together they set back on the course they had approached.
As the Three's journey continued back into the space they had come from, they broadcast their awareness of the Edge to any other Vessels or Bound Minds they could reach. Many would initially shirk from the message, thinking the three to be Fidel or some other violent faction. Others would simply deny the claims made by the Returners. But some joined, including GV-6, a Generation Vessel born from a world Seeded by GV-3.
The peaceful crusade would be forever altered by the contact at Alviva 203. An Ilvaithi cruiser exited warpspace in the system, just as the Returner Vessels were approaching. Contact between the First Race and the Second was fraught with problems. Vessel protocols initially lead them to attack, as they classed the strange Ilviathi ship as alien. When the Ilviathi fought back with surprising tenacity and neatly crippled SV-19, there was a period of interaction. The Vessels were surprised to discover that the Ilviathi were human, and allowed the ship to escape, after discovering more about Earth since they had left.
Following a period of contemplation, the Returners decided that their directives now lead them to overcome the other races and re-claim Earth for the original humanity. The peaceful Return became a military crusade.
As with all Vessel factions, the Returners govern their human subjects via a theocracy, ruling as machine-gods. Although the majority of the Returners are Vessels and therefore have a minimum of human subjects, some Bound Minds are allied to the Returner crusaders (usually via parentage) and lend their world's resources to the cause.
The Returners themselves hold to a form of the seniority rankings used in general Vessel interation, but rather than give seniority to the Vessels which were created first, the Returners give seniority to the Vessels which first joined the cause, with The Three being obviously the most senior, and forming the ruling elite of the cause.
Although the Three can somewhat direct the focus of the crusade, the difficulties in communication and the great distances Vessels are seperated by mean that often members of the cause are working autonomously, using only the loose directive that they must reclaim Earth for the First Race, and otherwise acting as they wish.