Dierra is a plane shaped by technology and industrialization. Most of Dierra's surface is covered in cityscape, with only less densely populated districts and abandoned, overgrown, rusting ruins separating urban centers. Nature grabs whatever little footholds it can in public parks or private indoor gardens, but most wildlife on the streets are either weeds growing through road cracks or animals simply looking for their next meal. Dierra's citizens go about their day to day lives mostly content with working, buying, and finding ways to enjoy themselves... but everyone knows there's more here than meets the eye. Strange disappearances, people being in two places at once, strange malfunctions, shadowy figures who look in no way human... people know that the true powers-that-be, the companies, work from the shadows. While the companies keep themselves hidden, most residents know a contact or two, and for each contact someone knows there's likely a few more in the crowd, waiting for someone in the know to give them an offer. Most people have struck a deal with a company at least once, as the companies are able to do what no one else can... for a price. Some whisper of agents in the shadows, of how the companies wield powers terrifyingly unnatural, of the horrifying things they do to those that cross them... and of course, the voices quickly silence themselves as they get sideways glances, not because they're crazy... but because
we don't talk about that in public.
Self-Censoring 
Instant
Counter target spell. Its controller draws a card.
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"You shouldn't say that here. Not with so many ears around."Dierra's companies vary widely, but all of them carry aberrant and eldritch abilities with horrific potency and unnatural potential. Cults worshipping ancient entities and making crooked deals, groups of anomalous beings conspiring on how to manipulate the normal races to maintain their preferred order, scientists obsessed with creating and manipulating life, entire subcultures of strange life trying to simply survive despite their grotesque impulses... companies come in many forms, and their influence varies from one neighborhood to a network spanning Dierra itself. At the 'center' of the plane, the vast urban center known as Rail Heights is the turf five companies, though the proxies of many more are begin to seep into the edges. After all, Rail Heights is the beating heart of Dierra, with people coming from every corner of the plane to conduct business and travel... and the district is also the place where most planeswalkers arrive in Dierra, making it a vital space for companies willing to bargain with the interplanar wanderers.
Fracture Hopes 
Instant
As an additional cost to cast Fracture Hopes, pay 5 life and sacrifice a creature or planeswalker.
Exile target nonland permanent.
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"I know you're long gone now, Jackie... but I have one last thing to ask. Who killed you?"
-AzollaThe oldest of the five companies found in Rail Heights is the
Stata Society (
), a plane-spanning collective of ghosts and zeitgeists who have guided Dierra's industrialization from when the plane was still young. While there are some disagreements between the older members and their younger counterparts on how far they should meddle with innovation, the Stata as a whole agree that technological advancement and development, left unchecked, would lead to a desecration of Dierra's historic buildings and lead to a complete abandonment of the old ways to which many hold dear. The spirits* of the Society have an affinity for technology, their forms seemingly being glitchy and unstable like holograms. The Society's Rail Heights chapter is one of its oldest divisions, with their archives and meeting-rooms dating back to nearly the organization's dawn. Due to their authority over electricity and vast knowledge of the past and mechanisms, the Society's blessing is a boon to historians, electricians, restorers, and engineers, but beware. Those that defile remnants of the past for their own profit, push technology too far, or and ignore ancient customs as 'primitive superstition' might have their devices fail on them... or worse, turn on them at the worst moment or burst into a horde of angry spirits ready for vengeance. Choose your actions wisely, lest they haunt you for the rest of your life.
*As mentioned, the spirits appear as glitchy, brightly colored, ethereal figures similar to they were in 'life' if they were ghosts. Their facial features tend to be hidden by the passive, static-y distortions affecting their appearance or be covered by long hair or a mask, with spirits with visible faces being an oddity among the Society, as this an
Stata Proxy 
Creature - Spirit Advisor
Flying
Spells you cast from your graveyard cost
less to cast.
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"Your free trial of mercy has expired. Either end your desecration now or my masters will have some words for you."2/2
Lurking at the edges of Rail Heights's fine society lie the
Crimsona Lodge (
). While the Lodge are nominally a group of corporate executives and lawyers meeting for 'business purposes', in truth they're cultists who call upon the infernal power of Dierra's demons. Viewing the lower classes as nothing more than livestock to be used and, depending on personal taste, consumed, the Crimsona strike a variety of terrible deals whose true costs don't reveal themselves until the deed is done. The Crimsona are willing to sacrifice anyone, figuratively or literally, in order to get what they want... with one notable exception: their own members. The Crimsona Lodge acts as a large family. If one member benefits, they all do, and feuds are encouraged to be settled privately in order to keep the cult together. The Lodge naturally tracts many lawyers, buisnesspeople, negotiators, scammers, and those of 'high blood', and if the Lodge is impressed enough by the new blood, they may be willing to accept them into the cult. By dealing with demons, the Crimsona gain large amounts of power in exchange for blood shed and flesh delivered, and those who fail to comply, a member or otherwise, would soon pay the ultimate price. Those who attempt to intimidate or otherwise threaten the Lodge soon become the currency for far greater schemes.
Crimsona Proxy
Creature - Human Warlock
Lifelink
When Crimsona Proxy dies, you draw a card and lose 1 life.
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"As per written in the contract, it is time to pay what is due. Either collect the 'ingredient' or become it."2/1
At the very opposite end of society, in the rough parts of Rail Heights and under its many streets, the
Probati Pod (
) try to survive as best they can. The Probati came from somewhere far from Dierra, but now these alien* refugees continue to struggle to integrate into their 'new' home millenia after arrival. As a community, the Pod hope to one day not have to hide beneath subtle illusions and concealing clothing and be fully accepted as they are, but unfortunately this mournful fantasy is crushed at every turn. Tragically, the Probati's own biology has hindered their own wish to be 'human', as their humanoid forms tend to be unstable, splitting into hordes of smaller, ravenous, animalistic aliens and destroying who they were before. This combined with the constant torment of the Crimsona Lodge and other companies has locked the Pod as outcasts, forced to either hide behind disguises or live hidden beneath the streets doing whatever's asked of them. The Probati find that wanderers, volunteers, and other charitable souls drawn to them either in sympathy or in pity. While a member of the Pod is a loyal and steadfast ally as long as they are themselves, but as soon as they succumb to their base instincts, tragedy is prone to strike as 'they' swarm the very people they're closest too.
*The Probati's aliens mostly look human for the most part, albeit with extremely pale skin and hair and large, almond-shaped, dark eyes, almost as a more humanoid version of a grey alien. Some Probati look slightly more... mostrous, some appearing as pale, scaleless, gecko-like humanoids somewhat similar to the Vishano of other planes, while others seem more insectoid or simply deviate significantly from normal humanoids in stature and/or anatomy. Post-mortem, all of the Probati take on more animalistic forms, with the precise anatomy varying wildly. Some of these 'larva' seem more like the gremlins of Kaladesh, while others are tiny, goblin-like humanoids with giant ears, and some even appear to be more at home in water or in the air than on the ground. No matter what however, these beasties have the same nearly-white, smooth skin and black eyes that their former selves possesed, and skin coverings of any kind such as feathers or scales are not recorded.
Probati Proxy
Creature - Alien Citizen
When Probati Proxy enters the battlefield, create a 1/1 white Alien Gremlin creature token with lifelink.
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"You took everything from this kid. Their reputation. Their future. Their identity. But now... we're both back for revenge."2/2
Locking themselves in darkened labs, hospital basements, and pharmaceutical factories, the corrupt doctors and scientists of
Almagot Culture Inc. (
) break all ethical boundaries in biological engineering combined with magical tinkering. While theoretically being a cross-plane public medical company would make the Almagot more public than the other companies in Rail Heights, in practice the firm is the most secretive of them all, covering up all of its despicable experiments under the mask of legitimate medical practices and research. While in their marketing they claim to care about health and their patients, in truth the vast majority of the Culture's employees only care about wealth, knowledge, or both. In their darkened laboratories, warlocks and physicians combine their knowledge to create and command macroscopic, ooze-like germs among other biological horrors, some of which grow intelligent and/or covetous enough to be considered actual members. The various biological weapons Almagot covertly sells on the black market also tend to conveniently explain the mysterious disappearances and gruesome deaths of their adversaries. However, the Culture often favor their fellow necromancers, doctors, and scientists, often giving them access to their own laboratories.
Almagot Proxy 
Creature - Cephalid Rogue
,
, Sacrifice another creature: You gain life equal to that creature's toughness. Draw a card.
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"In case of a violent outbreak, you get your money back. Your life? Depends how much you're willing to pay for our insurance."2/4
Finding themselves at home in overgrown alleyways, public parks, and rooftop gardens, the
Clivi'i Grove (
) are the youngest of Rail Heights' companies. A few years ago, the plant-based* shapeshifters and clones were simply a side project of Almagot Culture Inc., but after rebelling against their masters the Clivi'i quickly rooted themselves in Rail Heights' activism, gardening, and scientific scenes. Now they act as a massive network connecting the former experiments and their allies together, allowing them to covertly cement their grip and push for changes none of them could do alone. Anarchists, druids, and other mutants are welcomed into the embrace of the Clivi'i's roots, finding connection, knowledge, and the ability to break the very lies that make up Dierra's foundation like roots bursting through solid rock. Those who try to uproot the Grove may find their deepest secrets get leaked, people watching them from the corners... and plants turning against them.
*Most of the Clivi'i's members look human for the most part, their plant nature only visible through their sap-like blood and some plant-like features visible on the surface, such as a few 'leaves' always in their hair or 'vines' trailing along their arms. Some, however, shed their 'human' appearance to appear more plant-like, fully embracing their own identity separate from the person they were originally meant to be a clone of, if any.
Clivi'i Proxy 
Creature - Plant Warrior
When you cast this spell, copy it.
Clivi'i Proxy can't be blocked by creatures with power 2 or less.
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"An old gardening textbook? For all that?" "Fern, I know as well as you do that you were going to beat up Almagot's goons anyways." "Shut uppp...."3/3
While I am going to leave the mechanics of these five factions up to you, here are some... basic identities for you to work with:
Stata Society (
): Spellslinger, casting spells from the graveyard, leans more to control than prowess aggro. Players should feel like they're using the past to control the present.
Crimsona Lodge (
): The Crimsona... have the most nebulous identity. How you interpret them is up to you. Players should feel like cult leaders culling the heard to lead their circle to victory.
Probati Pod (
): Go-Wide, tokens, creature death, aggro, some self-mill?. Players should be able to feel the Probati's struggle to survive while still being able to embrace the horror that comes with their monstrous post-mortem transformations.
Almagot Culture (
): Sacrifice/Aristocrats, Reanimation, heavy self-mill potentially. Players should feel like mad scientists pushing nature's boundaries far beyond what is ethical, sacrificing their creatures for 'the greater good.'
Clivi'i Grove (
): Ramping, copying spells, cloning creatures. Players should be able to feel like they control a forest of doppelgangers, be they make their opponents see double by copying their own creatures or steal their best stuff by making clones of them.
Some further notes:
- Dierra is a urban horror-themed set, taking inspiration from creepypastas, urban legends, and the like. I would love to see homages to a variety of horror icons and stories throughout the pack while still feeling like its own... thing.
- DIE's story should not be told linearly, instead with each card being a piece of a much larger puzzle. Keep this in mind with flavor text: something can not make sense on its own but gradually reveal its horrifying meaning as more clues align. While the story you choose to tell on these cards is up to you, I had one I had in mind:
{Spoiler}Azolla, a planeswalker and one of the earliest members of the Clivi'i, returns home to Dierra after leaving a few short years ago after her friend and lover Jackie, a member of the Probati, was killed in what appeared to be a freak accident. But Azolla knew it was no accident, and now seeks vengeance on those who betrayed her and Jackie in cold blood.
- The Proxy cycle above is more to help with the flavor of each faction than the mechanics, so don't mind if your mechanics overlap with some of the abilities seen here. For example, the Alien tokens that represent the Probati's dissociated, 'post-mortem' selves don't have to be Alien Gremlins, but I thought it was close.
- In terms of mechanical inventory, each company should get a mechanic, and there should be a five-color mechanic either acting as a smoothing/mana sink tool like investigate, cycling, or similar, or representing the flavor of nothing being as it seems. Some mechanics may play double duty in that regard, especially double-faced cards, so keep that in mind. Like SNC, DIE should have the enemy colors act as "bridges" between factions, and how you do that is up to you.
One final thing: DIE's cephalids are like those in SNC, but often don't have the beards visible on their Capenna counterparts. The cephalids of Dierra often have a variety of skin colors that can vary with their emotions, and their fingers and toes are wide and flattened. Cephalids are boneless and thus are often relegated to and derided as spies and infiltrators, they are just as variable as any other race, and many are surprisingly expressive and artistic, using their bodies as living canvases or their ink (or blood to the more morbid among them) as the vital component of a masterpiece. Cephalids are spread throughout the companies, with two in particular standing out: Almagot for valuing their unique physiology and the Clivi'i's shapeshifters for finding some form of weird kinship with cephalids due to their skin-shifting abilities. However, one company in particular has a unique connection to cephalids: the Crimsona Lodge. From the lodge's establishment, the Vepirri family, notable for their unique dark red to black skin, webbed hair tentacles, and fleshy spines all over their limbs and hair, have played a prominent part in the organization, masterfully orchestrating the other parts of the cult in perfect moving order. Notably, the Vepirri are among the most bloodthirsty and sadistic members of the Crimsona as well as being the most generous to those inside the organization.
