Like the history of Skaianet Systems, the Homestuck Epilogues use analogy to give us insight into how Alternia operated.
Like the land dwellers and sea dwellers on Alternia, trolls and humans become the two races who are, in Equius’ words, obligated to be at odds. This parallel between land/sea dwellers and trolls/humans is actually foreshadowed pretty early in the comic, when Feferi’s lusus tells her she’s destined to UNITE THE TWO RACES. Feferi interprets this as obviously referring to the land and sea dwelling races, but it later comes true in her instrumentation of the dream bubbles that allow the humans and trolls to meet. This parallel is interesting enough on its own, because Feferi herself contrasts racial unification with the prophesied extinction of trollkind - i.e. Jane’s goal as Empress of Earth C - and it’s ghosts from Feferi’s dreambubbles that are able to turn the tide of the race war.
It’s Gamzee’s important role in the Candy version of the Epilogues that gives us the most new information, though, because it finally offers some idea of what the dynamic between the subjugglator Highbloods and the sea dwellers, who are described as two distinctly operating parties, particularly during the class war instigated by the Signless:
Combined with the fact that the land dwellers are described as a self-governing body within the empire that the Condesce controls by leveraging oppression upon through the subjugglators, the picture painted of Alternia’s political situation is a complicated one. But Gamzee - representing his ancestor the Grand Highblood and the rest of the purple caste - walks the circus tightrope between lackey to the Empress and leader of the oppressed by bEiNg PoLiTiCaLlY nEuTrAl, BrOtHeR. He’s able to act as the strong highblooded enforcer of Jane’s regime while also claiming to look out for the little guy (in proper juggalo fashion) - as symbolised by the dual aquatic and terrestrial nature of the Capricorn.
The nature of his religion - of course a parallel to the Grand Highblood’s position as an important figure in Alternian religion - also seems particularly geared toward manipulating trolls specifically, targeting their perceived prior sins as a race as something that needs to be ‘redeemed’. This could be taken as a sinister version of the real-world ICP’s practices, using imagery of gangs and violence to market their spiritual message to a stricken lower class, or more generally as a parallel to the opium of the people interpretation of religion; either way it gives us a lot to think about with regards to the role the subjugglators played among the rest of the land dwellers back on Alternia.