I LOVE this.
Good idea. It's just... I have no idea how or where to do this.
I'd suggest you keep the Horde control thing very vague and very light. The neat thing about "group minds" in real life is how ethereal they are. Ant colonies can perform quite complex group behaviors, but their is nothing in control. No ant issues orders or has any idea of the end goal of what it does or why it does it. They just do things, one after the other, and in some way that's hard to define it all works out right.
Applied to the Hordlings, no one Hordling should be able to gain control of the Horde. The Horde may sometimes appears to act with a definite purpose, but where that purpose or idea comes from and how the Horde is coordinated should be very mysterious things.
In universe, I'd suggest that Horde mind, Horde spirit, Horde instinct, and other terms all be used by various commentators. There are probably almost as many theories about how Hordes work as their are people who research Hordlings. Many probably think that nothing coordinates Hordlings, and that the theories put forth by their cohorts are nothing but the result of looking too hard, like people finding coded messages in magizines.
Out of universe, it's probably sufficient that we know that sometimes, in an unknown way and for unknown reasons, Hordes begin to act as if they were responding to an idea, group of ideas, or a spirit. Often, his spirit or idea would be one that was lost on the Waste, but sometimes it may appear to hale from elsewhere.
As far as Hordling advancement, I'd suggest two paths. The first might be overall Horde coordination. Their are many levels of group organization, probably starting with "mob" and moving up through the level of schooling fish and flocking birds, then through ant nest or bee hive, and finally up through the level of a brain (one would not necessarily be able to communicate with a Horde, even one as sophisticated as a human brain. After all, no one tries to communicate with you by interrogating individual neurons).
The second might be for individual Hordlings. It is possible that a Hordling with a particularly strong spirit might become a "lost idea" if destroyed on the Waste, preserved by the other Hordlings in its Horde and by the Waste itself. Organized Hordes might also include stronger individual Hordlings, like soldier ants.
You can set up a poll when you create a new thread.
Thanks, and done 
The first thing that popped into my head when I read this is Bacchae. Very angry, perverted Bacchae, but their evil counterpart nevertheless. Although I'll be the first to admit that any theory on the subject would just sound ludicrous.
Or maybe the Hordlings kinda "created" the Bacchae in the first place...
Well, the problem I see with "converting" anyone to the Horde is: Why haven't they been killed/eaten/ripped in peces in the first place?
Scenario... PC's see a huge horde rushing in their direction over the Gray expanse. Not feeling up to the confrontation and having no chance of outrunning the mob, they hide in the nearby ruins and hope to not get noticed. The horde rushes past, ignorant of the trembling mortals only meters away. Just as the heroes believe they've made it out, the fighter starts coughing. The coughing slowly transforms into a prolonged growl as his back sprouts foot-long thorns, his limbs 'break' to form an extra joint, and his now fang-filled face assumes a feral expression. He turns toward the wizard and cleric, grins, and pounces, his howl bringing the attention of the remaining passing members of the horde, which flood through the building and continue along their way, now with one extra member and short of two mortal impediments to their plan.
.... ok - with that image - I'm now for the rest of the day going to be trying to banish thoughts of Jackie Estacado stalking the lower planes. That's just a great concept and image, would be great written up as a chapter's advance fiction.
I think that specific image alone has a lot of potential, too.
Are there such things in D&D as "Darklings"? Let me think here--I think there could be a vast potential for either a PrC or monster type or something that can control the Hordelings like that. Or--
I'm not sure, but there's something really interesting in there--taking the imagery from that game as a starting point, I mean, and drawing on some of that for the Hordelings.
Dang it, Clueless, if I have to get a PS3 or 360 now just so I can play that game, I'm going to be very upset... and by upset I mean poor but satisfied. That looks awesome. Oh, and I'll get a little expansion of that above image for an intro to you soon.
Are there such things in D&D as "Darklings"? Let me think here--I think there could be a vast potential for either a PrC or monster type or something that can control the Hordelings like that. Or--
I'm not sure, but there's something really interesting in there--taking the imagery from that game as a starting point, I mean, and drawing on some of that for the Hordelings.
First thing that comes to my mind is a Night Hag grafting some hordeling flesh to an unsuspecting character, giving him extra abilities and a limited control and protection from surrounding hordelings but an occasional lapse in said control and a reversion into a hordeling mindset.
Something I've wanted to mention--
We might be missing a big opportunity, here.
There are no independent demons/devils/fiends out there. What I mean to say is--there are no fiends which can 'fill in the gaps', per say.
There's something to be said for the idea that Hordelings are just basically a bunch of independent operators, some of which group together because of similar traits (and perhaps Horde 'consciousnesses' form when Hordelings produced from similar types of mentally-inclined larvae gather together). To be more specific, a Hordeling is the mutated, twisted expression of an evil soul; much more than any other fiend, they're human evil personified--a person's twisted nature turned inside out and put on their exterior.
I dunno though, maybe it'd be better to go with the Horde-consciousness theme entirely D: Or the anonymous faceless evil expression.
Edit: What this would mean, however, is that--unlike other fiends (except maybe Tanar'ri, to an extent), Hordelings are completely independent and each a unique expression of evil. Or do Tanar'ri all ready take up this mantle suitably?
Good point there.
I always felt some kind of "no" when reading about how Yugoloths, Night Hags or whoever else controlled/enslaved the Hordlings. Now I know why: Their essential free nature really makes them special.
They might not gain individual power as easy as other fiends, but at least they're independent.
That's true for baatezu and tanar'ri, too - the difference is that the Hordlings take on a form of their own choice, rather than being shaped.
I say we combine it
Somewhat. They're given shape by the nalfeshnee, the tanar'ri judges. Later on they can break free of that, turning into whatever they want - but the question is, HOW free of it can they really become, once they're forced on that path?
The absolute uniqueness of individual Hordlings was always something I thought of as one of the basic elements of the Hordling race, distinguishing them from the other fiends...
There's something there, I think, yes--the idea that the Hordelings get to choose. It fits well with the theme of Neutral Evil.
Why would Hordelings be subsumed into a greater Horde Will? Because some of the beings 'choose' to lose their identities--out of guilt, out of pain, out of fear, out of a desire to belong, a want for oblivion (bleakers! dustmen!)--thus they become one of many.
Other Hordelings don't want to be lost at all, and become individual, perhaps even powerful fiends. No one judges them or determines their destiny--their forms are merely reflections of who they are. They've been turned inside out.
Some Hordelings are an expression of anonymous, faceless evil (a specific type of hordeling? One that's actually surprisingly common, and deeply seated in the Hordeling Will? Perhaps these ones all share the same murderous consciousness). Others are an expression of a particular evil being's individual nature (most are, in fact).
Most Hordelings don't work together well because they're all varied and all have different agendas; it's not that they're chaotic and hate oppression (some of them might); they're just not the same. Controlling or enslaving them as a race would be impossible--it'd be like uniting a bunch of cats.
Possible plothooks with this involve Yugoloth attempts to hijack the Horde Will variant of Hordelings, a particularly brilliant and savvy Hordeling trying to combine the Hordelings as a species (he's got his work cut out for him)...
The Hordelings are free to be whatever they wish--whether that wish takes them to losing themselves in the Horde Will or being individually evil and continuing their careers across the planes. As for Hordelings being trapped in that form, I actually agree--entirely. Because the Hordelings don't have a caste system--they are who they are. They can gain levels, sure, but whatever form they choose, that's who they become.
I'm imagining the anonymous-evil Hordelings as pretty common--perhaps the most common, given the Gray Waste's Fade effect. Little darklings, or something--black murderous humanoid shapes of fangs, hooks, claws, and death. All of them are unique, aside from the fact that they're basically just clumps of shadowy flesh with sharp-toothed mouths and razor-sharp nails--and all of them more or less share the same 'faceless evil in anonymity' idea. They're the souls that were completely lost to the Wastes, and became nothing more than expressions of anonymous cruelty.
Perhaps these are the ones which serve as the chief resource of the Wastes--their bones used to build houses and tools, their bodies burnt in fires, their flesh cooked as meat, sometimes kept alive as pets, guard-dogs, hordeling fights, or makeshift weapons.
Yes, I'm thinking of the Orks while writing this. But I think it's a great parallel. D:
Edit: I like the "Darkling" term, unless it's been used before, if so screw it. But I imagine these guys could be incredibly stylistic and give the Gray Wastes a lot of interesting flavor--especially when you consider that they're all basically anonymous, and have no regards for their own existence.
Kept as pets, whatever--when found in the wild they can be hooked together as a "Horde Will" or consciousness, and will do crazy things in tandem, like all lumping themselves together into one giant Darkling-thing. Or using themselves as ladders. Or just all leaping and grappling on a larger opponent at once, digging, biting, and clawing. When found alone, completely sniveling and cowardly--when found in packs, ferociously fearless and incredibly dangerous.
And they're everywhere on the Gray Wastes, performing all sorts of petty anonymous evils--stealing food out of your packs, attacking and running off with pets, so on, so on.
You and me both.
I'm a rather large fan of the comic (mmmm Jackie) - I was lucky enough to get to play a demo of the game - and it is... teh awesome.
re: "Darklings" - the phrase is rather well known from the comic book, so it might not be good to use it in this context. Too much of a chance of the assumption that it was picked up from the comic as opposed to independently evolved. I had linked to the video for the mood and atmospheric imagery - not to accidentally inject what is admittedly one of my favorite anti-heros of all time into the project. (Sorry joyblood! Opps!)
I wasn't even thinking about that game when I grabbed the name out of my head. I probably stole it from there--yeah, I did. Sorry about that, I do it a lot.
Well, something else, then--I still like the idea of the Gray Wastes crawling with these nasty sharp-toothed little monsters who represent anonymous evil and get employed as basically a renewable resource by the denizens of the plane, like trees and cattle.
Oh heck yes - that matches with what my mental images of hordelings has always been.
"Lurklings" might work as an original name--it's a play on words for internet forum anonymity, see?! See!? I'M SO CLEVAR 
:D
Sorry for posting so much--my brain's all fermenting and I need to let it out before my skull pops in a messy gush of bone, viscera, and gooey gray matter.
But I think Lurklings might work as a name--and it pays to keep in mind that they're just one type of Hordeling (albeit the most common, since most evil souls who end up here are just too petty and weak-willed to keep their individuality and become 'True' Hordelings, thereby being swallowed up in 'the Will'). Lurklings aren't as manageable, currency-wise, as larva (hence why Hags prefer Larva in general), especially since larva can easily be turned into Lurklings, but they're still an immensely important part of the Gray Waste's economy and ecology--in fact, they may very well be the Gray Waste's ecology.
And, hell, Lurklings can still be used as currency--they're just probably not worth nearly as much as a fresh larva (hey, maybe they use Lurklings for spare change )
I like it, except for the part where they choose their forms. I think that should be a reflection of what they are. Also, given that they choose to form hordes to get lost in anonymity and thus escape from their sins, there is ample explanation as to why there are multiple hordes. When hordes do form, however, and they do quite often, a horde mind/will/whatever emerges naturally.
EDIT: That was in response to Hippo's last doublepost. Wow, this thread moves fast!
Then we'll just have to pull a Glasya and turn you into a layer and your head into a fortress.
)"Keep the change. No, really." must be heard quite often in the Wastes. It is also kind of ironic that while the Wastes have strong ties to currency, gold coins, and banking (note the shape of the portals) through their original canonical evolution from the Greek Hades' domain, their currency is actually in living beings.
I don't want to be the spoilsport (wtf is with that word? never heard this before, thoug http://dict.leo.org/ tells me it means "Spielverderber) but all that thing about individuality totally runs against anything we said before. Being free of the influence of the other races? Sounds OK. More "Animals" (Lurklings) on the Outer Planes? A must! Individuals with completely free will choosing to become part of an anonymous Horde devouring everything on their way? Sounds like 4chan . . .
Actually, my idea for the faceless anonymous hatred was based off of 4chan's /b/ (and all those inspirational posters that says 'Anonymous Does Not Forgive'), so you're not far off the point. I actually think that's a terrific parallel, although it should not be the mold for the entire race (just the lurklings, and possibly a few other branches).
But there's something I need to address here: I didn't imagine that the petitioners turning into Hordelings got to physically choose what they became. I mean, you don't pop into a room with a helpful guide who says "Okay, you want to be a Hordeling with acid for skin, a lurkling--what?". When I said 'they choose', I meant that the choice is based on the type of person they are. It's more of a subconscious decision than anything else--if you're a sociopathic murderer, then your subconscious mind will reflect this and shape your body accordingly. If you're stricken with grief, your subconscious mind will draw you towards the lurklings, letting you find comfort and peace in anonymous hatred.
You choose, but not consciously; you simply become a reflection of who you truly are. In some ways (depending on your viewpoint), it's the best thing that could happen to an evil character--they get retrofitted with the body that best reflects who they are and what they want.
Okay, while I can somewhat appreciate the idea of the Lurkling 'caste' of Hordelings (I say somewhat because I don't want it to become a caste system like the other fiendish races), I'm still a bit confused as to how they fit in to the greater scheme. Hippo, could you define your idea of Lurklings for me, and how exactly they relate to the Hordelings at large? Because right now I can imagine a lurkling and how it fits into the plane, but not to the race as a whole.
You choose, but not consciously; you simply become a reflection of who you truly are.
Or what others think that you are. 
However, this way it seems to make sense. And yes, I know you refered to 4chan earlier (though I don't think everyone there would end up on the Lower Planes.. just.. some). Actually I have to resist to make any mention about 4chan being sort of a.. faction.
Idea: Hordelings left alone, degenerating, maybe after loosing one or two of their extremities.
Okay, honestly, I've just been riding by the seat of my pants as ideas come to me, so it's fair to call me on that. This is what I'm thinking:
Lurklings aren't really a 'caste', or a 'species' of hordelings at all. They're just something that's become so common among the otherwise amorphous and unpredictable Hordelings that everyone's given them a general name and come to expect certain traits from them.
Lurklings are petitioners and larva who, unlike most Hordelings, were subsumed completely by the plane's sense of ennui and despair. The result is that they're very weak--they possess no true sense of individuality, their qualities are very generic, and they're basically prolific as all hell (because most petitioners aren't strong-willed enough to become 'True' Hordelings).
The result is this glob of black shadow with claws, teeth, fangs, and who knows what else. Just like any hordeling, no two lurklings are alike--some are poisonous, some have wings, others are fish (think pirahnas! Little more than swimming mouths with teeth. No, seriously, that's all they are), et cetera, et cetera--just like any hordeling, you can't pin them down.
The thing is, they're pretty weak, especially when they're not with other lurklings (lurklings tend to group together for some unknown reason). So, basically, everyone on the plane just uses them for--well, everything. The hags turn them into food, mortar, and firewood (using various alchemical processes that they do their best to keep secret), they're employed as currency, bottled and sold, thrown as weapons, and even kept as pets.
Think of them as the most base, simple, straightforward Hordeling that can exist--they're still endlessly varied, but they're pretty much the lowest of the low, and thus everyone just generally started calling them by the same name.
Or maybe--and now I'm just flying off into la-la land, here--maybe some of the bigger, nastier hordelings are composed of dozens of lurklings. Or the hordelings can use lurklings as building material to literally heal themselves. A hordeling lost an arm? Grab a lurkling, jam it into the socket, turn it into a new one.
That might be a little too much, and a little too chaotic--but on the side, it would support that awesome PrC idea Iavas was talking about with grafting lurklings (or even hordelings) to yourself as a way to empower yourself.
The basic idea here is that because lurklings have so little individuality or will of their own, Hordelings can basically just scoop them up and use them as spare parts, or change themselves using lurklings as a base ("I need gills?" *snags a fish lurkling, rips its gills out, pastes them on*). The lurkling might get to make a will save to resist it, but most lurklings are doomed. Hordelings may be able to do this with any other Hordeling (it's how they basically 'evolve' and change), but usually run the risk of being subsumed by the person they're trying to subsume, because other Hordelings might have much better will saves.
Hordelings who do this too much might risk subsuming themselves in the anonymity of lurklings, though, and becoming nothing but a lurkling themselves--or maybe this is where Hordeling Wills come from (a hordeling that's broken apart by this process into dozens or more lurklings, all who used to be part of a whole, all still acting as a part of a whole).
Hell--maybe when Hordelings die, they break apart into their composite parts, becoming a bunch of lurklings with a basic Hordeling Will interconnecting them.
This idea might be way too trippy though, so take it with a grain of salt. A big one.
Or maybe--and now I'm just flying off into la-la land, here--maybe some of the bigger, nastier hordelings are composed of dozens of lurklings. Or the hordelings can use lurklings as building material to literally heal themselves. A hordeling lost an arm? Grab a lurkling, jam it into the socket, turn it into a new one.
That might be a little too much, and a little too chaotic--but on the side, it would support that awesome PrC idea Iavas was talking about with grafting lurklings (or even hordelings) to yourself as a way to empower yourself.
This idea might be way too trippy though, so take it with a grain of salt. A big one.
I like it! And not only because it supports my whole Ultramind thing that I was discussing earlier. They are seperate creatures just like they are seperate minds, but they can be either voluntarily or forcefully combined. VOLTRON, HO!
Hmm.. Because the hordlings seem so chaotic in appearance, it makes them kinda like gehreleths in a way. I feel that the idea of a supreme overmind makes them seem even more like the gehreleths as Apomps controls them similar to an overmind. Plus the hivemind makes them too much like the zerg, whil cool, is a little too unoriginal for my tastes. Besides they're neutral evil, they shouldn't all want to take orders and give orders however it is they act.
Ohh that gives me an idea, what if there is a sort of caste war going on within the hordlings, the hive minders are slipping closer towards law and the more fierce individualists are slipping towards chaos. While other hordlings who wish to remain neutral are fighting both while trying to garner a foothold as an empire to rival that of the 'loths. However the ones slipping are still very nuetral and refuse to be press ganged into either the baatezu or tanar'ri blood war. At least not without a fight. I feel we should make a few hordling heroes or at least powerful enough individuals to stand against the Arch Devils, Ultraloths and Abyssal lords. Without creating a race of beings similar to gehreleths but slightly less powerful.
Seeing as how the ancient baatezu and tanar'ri are no longer present. I think that 'loths might be a little more than concerned that now its there time to bite the dust and the horde to rule in their stead. Maybe thats why their runnin to gehenna. Then all of the lower, lower planes'd have their own unique fiend race. Baator: Baatezu Gehenna:Yugoloths Gray Waste:Hordlings Carceri: Gehreleths Abyss: Tanar'ri. As I said maybe a second blood war is about to begin this time for the control of purest evil. This could wrack the Multiverse!!!
Okay. Apologies in advance for repeating myself so many times--this is just my idea, and if everyone decides it's dumb and crummy and doesn't belong (or they just want to snatch individual parts out of it), that's fine. But I think it bares a full, detailed explanation here, because so far I've just been touching on it in two or three different threads, so a full and concise explanation of how I envision Hordelings--here and now--might be helpful. Anyone who's all ready got the full jist of what I'm talking about, Hordeling-wise, feel free to just skim it--there's nothing miraculously new being presented here.
Ignore or use to your heart's content!
My Take on Hordelings:
What I'm basically thinking about here are Hordelings with no caste system. There are basically two 'types' of Hordelings, but that's a bit of a misnomer because all Hordelings are unique.
There are normal Hordelings, which can appear as anything--reflections of a soul's inner self brought to the surface--and then there are Lurklings, which are souls that were very weak and incapable of rising above the Gray Waste's Fade effect.
Lurklings all have a similar appearance because there's so very little of their original identity left--it's been swallowed up by the Wastes. They're black, nasty, and have lots of pointy things (claws, teeth, whatever). They can have a multitude of unique traits or appearances (some might be fish--nothing more than a swimming mouth with tons of teeth--some might be trees with mouth-baring fruit--some might have bat-wings, others might move on all fours). They're pretty much considered 1) Dangerous pests (stealing food, killing wounded, gathering in packs to attack villages, sabotaging structures, gnawing on bridge supports), 2) An expendable resource (the hags have several processes to turn them into food, building material, potions, and even use bottled Lurklings as a form of cheap currency), and 3) Pets (guard-dogs, Lurkling fights, whatever). No one considers them a serious threat, though when you get enough lurklings together, they can do a lot of damage. There's probably quite a few darks about the lurklings, including rumors that they're all connected mentally somehow (Hordeling Will). Some even say that sometimes a consciousness swallowed by the Wastes can be shattered into dozens or even hundreds of lurklings, all of whom are connected. Regardless of any of this, ultimately, they are the petty, faceless evil of the Gray Wastes.
The rest of the Hordelings are souls that possessed enough will to maintain their individuality. Their power and appearance ranges wildly, although I'd say that stylistically, they tend to be darkish/monochrome in appearance and have lots of nasty claws and teeth. Very few have very humanoid appearances.
Being independent and possessing no caste system, there isn't any overall racial imperative like the Tanar'ri, Baatezu, and Yugoloth; the Hordelings basically just kill anyone who threatens their domination of the Gray Wastes and keep to themselves. Just like any species, some of them have agendas, and some of them try to unite other Hordelings to arrive at these agendas--there's no real 'chaotic' element among them to prevent them from working together--but the Hordelings have no real sense of collective unity beyond a basic 'defend our territory' instinct. What they do have is one very nasty ability: They can absorb each other.
A hordeling can absorb another hordeling into themselves, gaining their attributes, power, and knowledge. Hordelings do this with lurklings all the time to heal damage done to themselves or gain some helpful ability a lurkling might have ("I need gills." *grabs a fish lurkling*). Doing it with strong hordelings is dangerous because they could always manage to absorb you instead (and even if you are successful, you might end up with a chunk of their consciousness invading yours). This is very similar to the whole Vampire: The Masquerade diablerie process.
In addition, when a very powerful hordeling dies, there's a chance they'll split off into one lurkling for every hit-die. These lurklings form something of a collective consciousness, a 'Hordeling Will'--and, given enough time, they may be able to recombine and 'reform' into the original Hordeling (assuming they aren't all gobbled up in part by other Hordelings). And yes--some non-lurkling Hordelings are formed when one lurkling manages to absorb a bunch of other lurklings and actually becomes a 'fully fledged' Hordeling.
Anyway, what all this means is that although Hordelings have a very chaotic appearance (and mostly an anarchistic, apathetic society) and a ferocious appetite towards one another, aside from the ravening hordes of lurklings (wild ones attack on sight or flee if it's clear they can't win), they're basically a 'Don't-Bother-Me-And-I-Won't-Bother-You' race of fiends--there's probably a few dark plots being launched by individual Hordelings, but they're one of the few fiends out there that don't have any Great and Terrible Plan (tm) for the Multiverse. Most of them are content to stick to the Gray Wastes and kicking anyone's ass who tries to remove them.
They beat the Yugoloths out of the Gray Wastes. The Yugoloths, who have made multiple attempts to pry the Hordelings out of the Gray Wastes, just can't--because the Hordelings are too individualistic for any one strategy to work.
Hmmmmmm.
I like this, but I don't think all of this works as canon without breaking other ideas.
Have to think more about this, and will post later.
Okay now, finally read through the thread. It's all great stuff, but needs to be combined now into something we can use as canon - without messing up the already existing ideas and canon descriptions. I'll attempt that right here.
Hordlings are born from larvae (which are herded by Night Hags usually, though there ARE herdes of larvae without an "owner" found in the Waste).
Larvae with a weak will, or ripped out of their shell to early (by Night Hags), turn into Lurklings, the anonymous masses of the Hordlings. They're unique Hordlings like all the others, what's defining them as Lurklings is their lack of a real identity and a generally low power (3 HD should be maximum for a Lurkling). They are the "low-level fiends" among the Hordlings.
Lurklings are often used as the "expendable resources" of the Gray Waste, their bones transformed into firewood by the Night Hags, their flesh and souls used as food, and the entire Lurklings occasionally used as currency similar to Larvae. Since they are not as easy to use as larvae, they are more like the small change money than the shining gold coins...
The stronger ones among the larvae (maybe, in some cases, also the ones "pushed" by Night Hags) turn into "True Hordlings". They're comparable to lesser fiends of the other races, and those above, reaching up to the power of Abyssal Lords / Lords of the Nine, though THOSE Hordlings really are exceptions. (More about them in a few sentences...)
Hordlings generally see the multiverse in three categories: "I" as the individual Hordling, "It" as the Horde / Horde mind (more below...) to which they belong, and everything else. Everything else is best destroyed or ignored.
Hordes *always* create a Horde mind (official name: "Horde Will" or "The Will"; Hordlings refer to this as "It"). This is like a hive mind, but different: It's more like an instinctive spirit, which can be influenced by Hordlings of individual power (usually not the Lurklings), but also influences every Hordling in a Horde. This Horde mind makes the Horde act as a whole, but the fact it's almost impossible for a single Hordling to take full control of the Horde mind (at least for long) makes sure the Hordes stay as "chaotic" as they are known.
Also, the stronger and more powerful a single Hordling, the easier it can keep itself from being influenced by the Horde mind. So, even when a single Hordling manages to take full control of the Horde mind, that doesn't mean he's taken full control of all the Hordlings in the Horde.
There is *one* Horde mind for *every* Horde. There MIGHT be an "Over-Horde-Mind" connecting all Hordlings, but that is pure theory. As canon, there are as many Horde minds as there are Hordling Hordes.
Hordling Lords/Kings/whatever are individual Hordlings as powerful as the Lords of the Abyss or the Lords of the Nine. They could, theoretically, take control of a realm of their own, but such a thing has never been known to happen. Instead, those powerful Hordlings seem to prefer taking control of "their" Horde mind, with all the restrictions mentioned before.
Horde minds can develop powers of their own, which are both spiritual and instinctive in nature. That is, a Horde mind doesn't actively throw fireballs against a certain enemy. But a Horde mind might drain the land of life, or it might "infect" anyone coming too close with a Hordling nature, forcing the victim to run with the Horde and, if not removed early enough, turn into a Hordling themselves.
Hordlings are stuck with the original shape they get, which represents their evil inner spirit turned inside out. This is a good reason to work out individual Hordlings' shapes with much detail love, because working on its shape kinda means working on the Hordling's personality.
A major conflict for Hordlings is the inner battle of anonymity vs. individuality. The Lurklings have lost most of their individuality, becoming part of the anonymous masses of the Gray Waste. "True" Hordlings might keep their individuality, or parts of it, but it is a common battle: The Horde mind always instinctively tries to consume the individuality of all of its Hordlings, and a Hordling has been strong enough to resist that pull. This is comparable to an Abyssal Lord fighting against a layer he controls: The layer tries to consume the Lord while the Lord tries to force his will on the layer. It's just not so much of a "one on one" thing with Hordlings...
This one I'm not 100% sure about it yet, for it half-way goes against the "Hordlings are stuck" theme. I, personally, would prefer something more subtle/secret than "grabbing the limbs of your neighbour", on the other hand I like the idea very much because it fits the "Hordlings are raging maniacs" theme so well. Hmm.
Hordlings evolve not through changing their shape, but through consuming other Hordlings. They can assimilate both mental, spiritual and physical abilities, immunities and also weaknesses (the last one, in most cases, unwillingly), but it is always a battle: A Hordling trying to consume another risks being consumed himself instead, and also risks (once more) to lose his identity as he takes on more and more aspects from members of the "anonymous masses".
I want to clear up a small discrepancy in the reasoning concerning Gray Waste petitioners that I've been noticing. According to 'Planes of Conflict - Liber Malevolentiae', the default petitioners of the Wastes are weak grey ghosts, practically ethereal and completely emotionless except early in their existence. They are drawn to life as moths to a flame. Larvae, on the other hand, are said to be either the stronger of willed petitioners or victims of the Night Hags' nightmare ability. 'Faces of Evil', on the other hand, says that larvae can appear anywhere, not just the Gray Waste, and are simply the spirits of particularly evil mortals.
Personally, I would ignore that latter bit. It just conflicts too greatly with the fact that on Baator petitioners are said to appear as nupperibos and in the Abyss as manes. I want to suggest a small change to the above canon so it fits with the theories concerning the Yugoloth 'birth through cleansing'. There should, indeed, be two kinds of larvae - the weaker chaotic/lawful evil ones and the stronger neutral evil ones. The latter are created by Night Hags' stealing a mortal soul. The former, however, are the byproducts of the Yugoloth cleansing process. The 'loths steal a bit of lifeforce from the Plane, and thus its petitioners. The robbed petitioners, having lost part of themselves and the ability to feel despair, are instead reborn as the weaker chaotic/lawful larvae somewhere on the Wastes. Perhaps this is so because the 'loths do this through a haglike process... who knows.
Canonically, hordelings are simply really strong petitioners (PoC), and do not arise from larvae but rather from the mass of shades. The lurklings, perhaps, could be hordelings that have risen from imperfect petitioners... larvae. That is why they are weaker but still able to fight off the despair. This makes hordelings more native to the Waste than the Yugoloths, being unrelated to the 'loth created larvae.
Finally, the way I see the hordeling psyche working is not in conflict between its individuality and horde-will, but rather in a strange balance between these two seemingly opposite forces. All hordelings are individuals, evil and self-serving through and through. However, they realize that they are weak when compared to your average Baatezu or Tanar'ri or Yugoloth. Sure, they can take out a mortal basher, but even a Vrock would pose a problem one on one, not to mention a Balor. So, their self-serving mind instinctively drives them to form hordes. It is a self defense mechanism. Once a horde is formed, each member still retains its own individual thoughts and desires. Its instinct, however, becomes one with that of the horde. Therefore, the horde is driven on one impulse, but each member still has its own unique logical reasoning.
I'll admit - I like the idea of a hordeling, in essence being stuck in his form. It is a direct reflection of self - and unless self changes (highly unlikely) - nothing else will. It strikes me as fitting that a hordeling may become king of his horde, but still hold the same form as when he was 'born'. Almost as a point of pride 'I was good enough *already*'. It's a very human (real world) quality - that he can't change the hand dealt him.
It would make them one of the only races in the DnD world that do not in some way 'sculpt' themselves to be better. After all, how many prestige classes are all about the grafting or the becoming an outsider? How many yugoloths came to the night hags to be *changed* because their original forms were not good enough? It's a very common thing to do - physical upgrades.
I would restrict hordling evolutions by consumption to strictly non-physical changes: mental, spiritual, powers and immunities. Physical evolutions - new limbs, gills, etc - are temporary as their body rejects the 'not-I' change.
One great and imageric way to limit this sort of thing is to claim that any time a Hordeling consumes/grafts another Hordeling to their body, the other Hordeling still maintains their individuality--and is constantly struggling to get free (unless the graft was consensual).
Imagine a Hordeling in the middle of the fight suddenly undergoing this terrible, tremendous strain, twisting and writhing as one of its arms literally rips itself off and promptly scampers away.
Gah! That's the type of imagery that I just love. I think it gives hordelings far more flavour than your typical rampaging orc-horde with an outsider shell and random features.
It also opens up the possibility for Hordelings who have consensually grafted themselves into one (an entire city made of Hordelings working together, grafted into a singular settlement--something like this was mentioned in another thread) for added power and protection. And it makes that whole 'Horde Will' concept a lot more visceral.
Important notes; I'll sift through them soon. I have to admit the one resource about Hordlings and the Waste that I lack is the Planes of Conflict box.
I'll have to think about how your suggestions fit in with the status quo we agreed upon, the old canon, and the Tiny Little Secrets (tm) that I have for this project that I didn't spill yet...
Wait, you have Tiny Little Secrets (tm) that you're not sharing and that could possibly affect the very nature of what we're doing!? Travesty! Insanity! Evil! Somebody fetch me my torch, I'm going mobbing. 
Naaah, it's more like what you're doing is going to affect the Tiny Little Secrets (tm), so you can let your creativity run wild now, while I still have my future plans for this project...
Random idea, don't know if it even fits with the direction the project is moving (it goes so fast!) but here it is:
Because of their unpredictable shapes, sizes, and powers, it is very difficult to establish how strong a Hordeling is at first glance, even to another Hordeling. Therefore, most hordelings are very secretive about what they can do and are always on the watch to discover what other hordelings are capable of. Because of this, most Hordes only contain hordelings of about the same strength, say + or - 2 CRs.
Say that the base CR of a Horde is 6. That means that Hordelings of CRs 4 through 8 would be readily accepted. Most of these hordelings will not destroy one another wantonly because there is a good chance that they would be injured in the process even if they do win, and another hordeling would just finish them off. Any Hordeling weaker than that wouldn't last long as it would be eaten, randomly killed, or otherwise disposed of because any member of the Horde could and would suffer no consequences. And Hordeling much stronger than the Horde's accepted range, as soon as it was apparant, would be set upon by the rest of the Horde and killed because it is in their best interests not to have something around that could kill any one of them it felt like at any time.
Sometimes a weaker Hordeling that looks impressive can survive in a higher CR horde by bluffing its way around, or a much stronger Hordeling that doesn't look so impressive on the outside may join a weaker Horde for its own purposes.
If anything resembling this process turns out to be the way it actually works, then if there really are any "Super Hordelings" of Layer Lord level strength, then either they probably wouldn't look that impressive on the outside and run with lesser packs, or they are solitary creatures that are occasionally approached by lesser Hordes for some specific purpose, or they all travel in one particularly small and dangerous Horde of their own.
I imagine Lord level hordelings as something along the lines of a constantly mobile Tarrasque with an infinite amount of land to roam.
Kinda like John Carpenters The Thing. Sounds really awsome. Plus it would allow the more powerful hordlings to gain an advantage if they were in a tight spot. They would be almost killed, then they'd cut their losses and flee with whatever limbs they could find and reassemble somewhere relatively safe. However not all evil likes to reassemble,and has its own priorities. So the limbs could fight to become a different entitiy altogether. Hmmm..
I hope I'm not posting too much, but here is what I imagine would happen if a hordelings keeps adding lurklings to itself until it becomes one huge monstrosity: http://www.studiodaily.com/main/technique/casestudies/8445.html
That is, of course, if hordelings looked like people and were after beer.
@Hymneth:
I like that. Still, Hordlings that gained some control over the Horde Will should, at least in some cases, be able to find out something about their fellow Hordlings by "looking into the Horde Will".
I'd leave this as an individual Hordling decision. Most Lurklings probably don't care enough for that. The more powerful Hordlings might not care, or they might care to protect themselves, or even to see which Lurklings might fit well as an extension to themselves
While I understand your idea, I think it takes a bit of the Hordling flavour away. I, personally, love the idea that you never know what kind of Hordling you meet. The one fiend of that Horde you're battling right now might be killed with a single sword slash, the other then might be as hard an enemy as a balor. Or worse.
I really think Hordlings accepting any other kind of Hordling in their Horde gives a special touch to them, and makes them distinctive from, say, a tana'ri Blood War army.
Once more, I think that'd kill a bit of the flavour.
Imagine Graz'zt with a Hordling nature, just that he doesn't rule over three layers, but over a Horde of, say, three million Hordlings. And due to the restrictions of controlling a Horde Will, the massive Horde still has a good deal of its own will, so that every decision our Graz'zt-Hordlings want to enforce is a battle of willpower: Hordling Lord vs. Horde Will.
I mean, imagine what might happen if such a Hordling Lord decided to invade a Prime world through a portal...
I wouldn't make it canon either. It was meant exactly as a contradictory legend (as hinted by the "Some bloods say..." part). Thanks for the feedback.
Squaff: Yes, every name has its merits and its faults. I was just throwing those out there as a suggestion, say a nomination, that could be voted upon later. May I suggest, therefore, that joyblood make a poll of this so that we can officially vote for the name of the hordeling consciousness among all the suggested ones?