The Alternian Empire supposedly conquers aliens, but do we have any confirmation these aliens even exist in their universe? The troll kids have been indoctrinated enough to not be surprised by meeting aliens, but we never see or even hear a description of any, except the ones from actual other universes, which is weird because one would think they'd use alien slave labour or eat them or something. It wouldn't be OOC for the regime to be lying about the aliens, would it?
We’ve only ever seen Alternia. Alternia’s a space-faring intergalactic empire, if they spread outwards from Alternia and have conquered as much of the Galaxy as is implied, Alternia sits squarely at the centre of said Empire. Have you seen how brutal they are? They already have their slave labor on the lowblooded members of their own society, they likely just. Destroy everything in their path with no prisoners taken. Aliens would be much more likely to appear on the outer rim of their System than going right to Alternia. There’s really no reason why the regime would be lying about Aliens, when we do know the only reason Condy couldn’t make it in time to stop the Vast Glub was because she was conquering planets really far away, and she’s got enough expertise conquering alien species to single-handedly conquer Earth with just herself and fear.
It still seems a little weird that, if that’s the case, none of the trolls we’ve seen have even mentioned any previously discovered alien species (except the cherubs but I don’t think they’re a naturally occurring species; they’re so heavily tied to the game that I’m pretty sure they’re from another universe entirely or maybe created by the game itself). One would think they’d say “oh, you’re an alien? you look just like the ones from planet XYZ” or something. Even if there aren’t any aliens on Alternia, surely the propaganda about them would at least say what they looked like? And I was imagining they were using the possibility of conquering aliens as a way to encourage trolls to agree to leaving the planet.
That’s assuming Aliens are easily categorizable, all three Alien species we see in Homestuck are Humanoid but, if Condy’s expanded the Empire so much, chances are there are hundreds of different Species with their own special stuff and all. Also Hussie wouldn’t give THAT much thought to the empire, let’s be fair.
Also Trolls don’t need encouragement to leave the Planet. They leave the Planet. Or they die.