This is probably one of the biggest mysteries within Homestuck/Hiveswap. An entire caste of people was wiped out in a genocide whether it happened in a short span of time or over time is still unknown.
WARNING: There is mention of totalitarianism, Nazism and genocide.
WHAT DO WE KNOW?
Not a lot but probably enough so we could come to a solid conclusion to their decline and total extinction. Most information that is known about the Limebloods is mostly through the Extended Zodiac and Calliope.
• They had unusual names compared to other trolls.
• The Signless, Karkat and Kankri are known mutants of the Lime Caste (Karkat and Kankri being post-eradication – I’ll explain later)
• Out of all of the lowblood masses, Limebloods posed the biggest threat to the Highbloods
• They were hunted to extinction
• They have magnetic personalities
• They’re passionate lovers
• It’s heavily speculated that they possess powerful calming abilities due to the panel KARKAT: CONSOLE GAMZEE which shows lime coloured text when Karkat is calming down an enraged Gamzee.
• The Caste was incredibly common
WHAT CAN WE GATHER FROM THIS?
They compiled a large number of the population which naturally meant that there was more genetic material going into the slurry. We know this because they tended to have magnetic personalities and were passionate lovers. Limebloods were most likely preferred Pale material due to their calming abilities meaning that most of their quadrants would lie with the Highblood end of the spectrum. Then something must have been a catalyst for Her Imperial Condescension to order for the extermination of an entire caste.
WHY WERE THEY ERADICATED THEN?
That’s the dicey part of Limebloods especially since we don’t have many notes on their actual eradication beyond being hunted till extinction. But the answer most likely lies in Alternia’s actual government system and Alternian History – the Summoner’s Revolt in particular.
We know for a fact that Alternia, in a strange sense is a monarchy and a harsh one. Then there is mention that Trizza Tethis runs Alternia as a totalitariate state. Funnily enough, though The Condesce has been the dictator of sorts far longer than Trizza, the only reason why it’s more obvious with Trizza is that we have never seen HIC ruling when the adults were still on Alternia. Anyway enough of this blurb bullshit. Take notice how I bolded Totalitariate State, this is because Alternia meets the criteria. According to the historian Friedrich, there must be six-point criteria to qualify as a totalitariate state (I’ve written these points simply):
1. An official ideology which covers all aspects of a man’s life and society must adhere to it.
We can see this in Alternian Society as lowbloods are considered the lowest of the low and everyone has an assigned role for example Jades who are clustered must work on a planet cut off from trolls of other castes and Teals must work within legislacerator terms.
2. A single mass party consisting of a small percentage at all times who are dedicated to the ideology.
It’s simple about who qualifies for this point, it’s the seadwellers who are literally the most elusive and least populated social group who just so conveniently sits comfortably at the top of the food chain.
3. A near monopoly control of all means of effective combat
HIC does, in fact, have this, it is literally every possible adult troll who are made to leave their planet as soon as they’re an adult.
4. A near monopolised control of mass communication
Xefros states that Dammek made mention that there is likely someone monitoring all means of communication in case of a rebel which makes sense to be cautious. This is further solidified in Tyzias’ bad ending route when she mentions that she couldn’t put her handwritten notes onto Goregle Docs (Google) which then it is stated that someone is most definitely monitoring the system.
5. A system of terroristic police control that is used to threaten potential enemies of the state and is targeted towards selected classes or groups of the population
It’s quite obvious that this is the drones and the legislacerators to an extent. This dot point is a potential hint towards the Limeblood genocide since in basically all totalitariate societies there is some part of society that is openly discriminated against (most famously The Holocaust is a prime example of this).
6. Centralised Economy
Since we know jack shit about the economy let’s just leave this for now.
THE SUMMONER’S REVOLT
Basically, sum up this revolt, The Summoner was a bronze cavalreaper who rose to be like a commander of the cavalreapers and he had wings. When he caught wind of the Signless’ teachings he led a military revolt against the system. Now this revolt must have very effective and near successful because of the aftermath of that revolt, HIC literally banished all the adults off the planet.
SO WHEN, HOW AND WHY DO THE LIMEBLOODS DIE?
Given the evidence and the historical and contextual information that is provided, I believe that the Limebloods were killed after the revolt but before the adults were exiled. I personally don’t think that they died before the Signless because we have Karako – who is cullable since he is remarkably smaller than other purplebloods his age which emphasises that he may as well have some growth-related mutation. This instance would most definitely apply to Signless since, realistically, mutations are bound to happen caste eradicated or not. That’s the when.
The how is quite foggy but I can imagine that witnessing defeat when something was close to failure would be enough to break a persons’ spirit meaning that they might as well comply to save their skins. So I wouldn’t be surprised if they were rounded up like cattle and shot at point-blank range. My other theory is probably something someone has already mentioned but this is quite prevalent in Alternia anyway, Social Darwinism which means that specific traits are taken out of the genetic code – most well-known examples is Sparta and Nazi Germany.
They were killed because of how powerful and how populous they were – which could be the reason as to why the purples abide by the system but that’s a theory for another day. Under the terms of battle Limes would naturally be informant brokers, infiltrators, spies and assassins all thanks to their calming abilities (which I suspect can steady a sporadic heartbeat to the point where it flat out just stops working) and magnetic personalities. Before the Empress gained the upper hand I can actually see the Limes being one of the biggest reasons as to why the revolt was going in the Summoner’s favour. So logically when HIC won the war she would try to eradicate the biggest threat, in this case, would be the Limes, in my opinion, the second caste to be fully wiped out if it was to happen again would be purple but purples for another day.
Also on the note of the revolt, if @CynicalBonehead’s and @Banavelope’s theory about Limes being freshwater trolls is correct (which I hope it is as part of the Lime caste myself) then it would give HIC more motive to commit mass genocide since, in a sense, Lime’s controlled the waterways.