[dyson sphere with demons thing]

[Kappa]

So once upon a time, I wandered through the living room while my dad was watching a weird 3d-animated movie on Netflix. And then like a week later I wandered through the living room and he was watching a different weird 3d-animated movie on Netflix. And these concepts each sounded like they would make for an interesting glowfic premise, and they merged in my brain into a bizarre conglomeration which proceeded to get even more interesting.

The shows were Gantz and BLAME. One is about a video-game-in-real-life scenario in which an ominous black orb commands you to fight invading demons and offers prizes like fantastically powerful weapons or the resurrection of your fallen comrades in return for demon-related bounties; the other is about a post-apocalyptic society of nomads living in a derelict megastructure, scrounging resources from the ruins of civilization, hunted by a deranged security system that seeks to protect a group of people who no longer exist.

The bizarre conglomeration, then, is about a post-apocalyptic society of nomads living in a derelict megastructure, hunted by bands of roving demons, with their tribes and villages defended by ominous black orbs that recruit people to fight the demons and offer weapons and resurrections in return for collected demonic essences. The security systems of the derelict megastructure are sometimes helpful, sometimes not.


The derelict megastructure is a Dyson sphere, constructed using a form of light-based magitech that centers it on its star and powers it via a feedback loop: the star's light is absorbed by the sphere's inner surface and fed through its major systems, then recycled to feed the star in turn. Very little energy escapes this vast shell, but it's net positive in usage vs production; left alone, it would keep going forever, providing food and water and light and shelter and comfort for potentially quadrillions of inhabitants.

Unfortunately, it was not left alone.

I'm not sure exactly where the demons came from or what their deal is, but they managed to wipe out the original population of the sphere almost completely. The remnants of the sphere-building society didn't have enough expertise between them to continue understanding and maintaining the systems of the megastructure; things started breaking down and going faulty. The megastructure was well-engineered enough to last a very long time with very few catastrophic failures even on a maintenance regimen of "no", but with demonic rampages to deal with on top of that, it's suffered some serious issues.

Given the sheer size of the sphere, it's entirely possible for alien explorers to land on it somewhere, investigate, get murdered by demons a little, find an orb with which to protect themselves, settle in, colonize the place, and completely fail to even notice that there are still any survivors anywhere inside it for the next hundred years. And of course the survivors could easily end up being wiped out by assorted catastrophes anyway. So the sphere will be available as a setting in both "inhabited" and "uninhabited" flavours.


The way the orbs work is approximately like so:

• The orbs are glossy black spheres, 1m in radius, which habitually float a few inches above the floor or ground. Unattached orbs will roam the megastructure at random in search of non-demons to protect.
  
• A tribe or settlement must bond themselves to an orb to receive protection. If the population of the group is less than 5, all members will be listed as active protectors. As the population grows, the orb seeks to rebalance the proportion of active protectors using these guidelines:
  • The minimum number of active protectors in a group with a population less than 120 is 4 or one-tenth of the total population (rounded up), whichever is larger. The minimum number of active protectors in a group with a population greater than 120 is 12 or one-millionth of the total population (rounded up), whichever is larger.
    
  • If any active protectors are children according to the developmental timeline of their species as best the orb understands it, decommission the youngest as soon as restrictions allow. (By the orb's standards, humans 14 or younger are "children", while humans 15 or older are "adults"; Amentans 3 or younger are "children", while Amentans 4 or older are "adults".)
    
  • Always accept (adult) volunteers.
    
  • If the number of active protectors is below the minimum, recruit a new one, choosing randomly from among adult members of the group if any are available. If the group has no un-recruited adult members, recruit the oldest child. Repeat until the minimum number is met.
    
  • If the number of active protectors is above the minimum, offer all active protectors the opportunity to be decommissioned.
• If the population of an orb's bonded group reaches 12 million (so that the minimum number of active protectors gets to be higher than 12), the orb will seek to find or create another orb to share the group with. Multiple orbs sharing a group will maintain and deploy separate teams of protectors, but all draw equally from the same population, calculating minimum team sizes according to a new formula which usually leaves them set between 6 and 8. Orbs prefer to share populations so that the number of people per orb is between 6 million and 12 million. If the population shrinks so that there are fewer than 6 million people per orb, one of the orbs will disengage and leave.
  
• Active protectors have powers that behave in many respects like being a video game character.
  • They have an 'on-duty' and an 'off-duty' state. Off-duty, they are more or less like any ordinary person of their species, but they don't age and any injuries they sustain will heal in their sleep. When they go on-duty, their ordinary clothing is replaced by protector gear, and their other powers activate.
    
  • On-duty protectors have an inventory of weapons and other useful artifacts which they can summon instantly to hand or return to storage at will. These items are only usable by on-duty protectors, but can be freely traded between them and safely handled by civilians if necessary.
    
  • On-duty protectors wear a glossy black bodysuit which is inseparable from their skin. They do not need to eat or go to the bathroom. They can equip armor from their inventory at will; it will appear over the bodysuit, replacing preexisting armor if applicable.
    
  • When the orb senses demonic activity near its bonded group, it will set its protector team's status to on-duty and teleport them to itself for a pre-battle briefing, waking them from sleep if necessary. After a short description of the situation, it will teleport the team to the site of the demonic activity; once all demons within range have either fled or been killed, it will teleport the team back to itself for the post-battle debriefing, then allow them to go off-duty. Teleporting to the orb heals the team of all injuries, so as long as they remain alive through the end of the battle, they'll be fine afterward.
    
  • When an on-duty protector kills a demon, their protector gear automatically collects that demon's essence and stores it in an account with the orb. The more powerful the demon, the more units of essence it yields. Essence is split between all protectors who damaged that demon, in approximate proportion to the amount of damage, weighted in favour of the person who dealt the killing blow. Outside of battle, protectors can use the essence in their account to purchase equipment, upgrades, and other useful things from the orb.
    
  • While a person is an active protector, the orb maintains backups of them. Restoring a person from backup is costly but possible, and resurrections can be purchased from the orb through the essence exchange system. It's even possible to resurrect people from the orb's previous teams, before it was bonded to its current group. Orbs sharing a group also share all of their backups and access to their essence accounts, and they retain that shared access when they go their separate ways.
    
  • Active protectors can freely go on- and off-duty at any time in their day-to-day lives, but must remain on-duty while deployed by the orb to a battle.
• If an orb's entire team is killed in battle, and the orb has enough essence stored in their accounts to resurrect them, it will do so. If not, it will recommission any adult retired protectors in the group, then search its archives for dead protectors with enough essence on file for a resurrection and resurrect those, then recruit new protectors by the usual procedure, until it reaches its minimum team size, at which point it will redeploy the team to the battle site.
  
• If an orb detects multiple demonic incursions in its area of influence, it might split the team to handle them (in sub-team groups with a minimum size of 4), or deploy to each site sequentially. If the team is already deployed and a demonic emergency occurs elsewhere, the orb will contact other orbs it has shared populations with in the past and ask them to deploy their teams as needed, which they will do if their teams are not otherwise occupied. If a demonic incursion seems too powerful to handle with a single team, the orb will likewise request assistance. (Multiple orbs sharing a population will deploy all of their own teams before seeking help from outside the current network.)
  
• A decommissioned protector can return to active status at will, and will be handled as part of the active team if they join a battle this way. Someone who has never been a protector must physically approach the orb in order to volunteer, but it is possible to join a battle that way as well, if one is ongoing at the time.
  
• Although orbs technically have no range limit, an orb will prefer to settle somewhere close to a high concentration of members of its bonded group. It will levitate or teleport to follow its group if they move their main settlement from one place to another. If the group splits into multiple subgroups which live separately from one another for an extended time, the orb will contact any unattached orbs it is aware of and split custody with them appropriately, or create a new orb if it can't find any after a long time spent looking.
  
• Simply living in a settlement defended by an orb for a few days is enough to add a person to that orb's bonded group, transferring custody from a prior orb if applicable. The only way to completely leave the jurisdiction of the orb system is to wander alone for several weeks: after about thirty days spent outside of defended settlements and unaccompanied by any other orb-bonded people, your orb will drop you from its registry - unless you are or have ever been a protector; even after decommissioning them, the orb system refuses to deregister those completely. (This is partly to prevent accidental resurrection-forking of decommissioned protectors.)
  
• Orbs can communicate with other orbs if they have ever shared a population, and can relay messages from one such acquaintance to another if those orbs are unable to communicate directly this way; but it's possible for an orb to be destroyed, and although rare, this has happened often enough to fragment the orb network into a multitude of separate pieces.
  
• Creating a new orb costs an amount of demonic essence approximately equivalent to a few dozen resurrections. It is therefore not done lightly, but an orb will do it if necessary to maintain a proper watch over populations it is aware of.
  
• If a wandering orb finds a group of undefended people, it will begin to follow them, choosing the subgroup with the larger population whenever they split. After following them for three days, it will become bonded to them and begin recruiting protectors. An orb cannot bond to a single individual this way, and will wander away if thwarted by a thorough dispersion of the group.
  
• If two groups bonded to unrelated orbs meet and merge, the orbs will merge their bond and share the larger group between them.
  
• Although their primary purpose is defense against demons, orbs also have a few other useful functions. They keep an excellent up-to-date census of their bonded population, of course, and maintain maps of recently visited locations. An orb bonded to a nomadic group will offer advice about where to go in order to find useful resources and avoid demons.
  
• Although orbs can communicate in a limited fashion, they are not sapient and do not have minds. Their level of awareness and complexity is similar to a very sophisticated video game with a little bit of magic to patch particularly important gaps in understanding.

Demons usually appear shrouded in a concealing veil of magic which makes them difficult to detect, affect, or examine by mundane means. Active protectors can straightforwardly see through this veil, and demons are plainly visible, audible, etc. to them; however, as a consequence, demons can sense the location of active protectors and will always know where to find them unless they are on-duty and making use of stealth equipment.

To ordinary people, a demon looks like a hazy cloud of ominous darkness and noxious vapours, and a demonic attack looks like several such clouds descending on a group of people and tearing them limb from limb by unclear means. Even if someone manages to get in a lucky shot on a demon with a mundane weapon of some kind, it's unlikely to harm them; you could think of them as selectively intangible, able to affect the world around them without being affected in turn, although only a few types are able to walk through walls.

To active protectors, a demon looks like a haphazard collection of body parts put together without much regard for normal rules of anatomy. Demons tend to take forms that mimic the plants, animals, people, and objects they have encountered: one demon might be a giant spider, another a swarm of disembodied human heads with improbably tiny bat wings, another an enormous snake with six lion legs on its left side and five dog legs on its right, another a two-headed vulture with a blood-red peacock's tail, another an oak tree shuffling around on its roots with twelve oversized octopus tentacles spaced evenly around its trunk, each ending in a razor-sharp knife blade.

Demons feed on fear, pain, and death. A demonic attack will first seek to prevent victims from escaping, then torture and terrorize them, then kill them one by one, saving the most terrified for last. The majority of demons are nonsapient, but most large groups of demons contain at least one sapient member, who assumes the position of leader and directs the rest to behave more strategically than their instincts alone would dictate.

Sapient demons also tend to develop individual approaches to predation, both in terms of capabilities and in terms of preferences. They can learn to manipulate their natural magic in ways ranging from the catastrophic to the subtle, throwing enormous fireballs or freezing the blood in people's veins - but perhaps the most terrifying of the sapient demons are the ones who have learned to conceal their demonic nature, take on the form of their prey, and hide among them for as long as several years. They can pass inspection by the orbs well enough to become registered members of a bonded group without being found out, but if any such demon is ever randomly selected for protector recruitment, they will die instantly and yield all their essence to the orb.

(The other main use of demonic stealth powers is in kidnapping handfuls of humans at a time and concealing them from their bonded orb's locator function in order to have some peace and quiet in which to make a slow meal of them. Less-powerful sapient demons might only be able to conceal one or two humans at a time this way; the most powerful can hide as many as fifty or a hundred.)

When there is no prey nearby, a demon will go dormant, hibernating for potentially thousands of years until they sense creatures with some form of nervous system in range and wake up to attack them. Orbs tend to avoid these, especially the more powerful ones, but an orb whose team is low on essence might deploy them on top of a medium- or low-power dormant demon as a 'training mission'.


The interior and exterior surfaces of the megastructure are not habitable; the exterior is bare metal facing vacuum, and the interior is tiled with energy collectors. All the interesting stuff is in between, within the volume of the shell itself. Gravity points inward toward the star, and in most areas is comparable to Earth standard, although some sections use different settings or have malfunctioning gravity control.

Some areas mimic nature, with artificial suns suspended over vast sprawling artificial landscapes, powering entire ecosystems with their recycled light. You could wander for months inside one of these enclosures without ever reaching a wall. The smaller ones are usually a few miles across; the largest ones have multiple continents, and could easily rival a planet for habitable surface area. Most of them have reverted to wilderness preserves even if they didn't begin that way, but a few still contain usable ruins with functioning relics.

Some areas are more urbanized, with stacks of apartments connected by lifts and corridors, interspersed with parks and restaurants and libraries and museums. Most of the machinery in these cities has stopped working one way or another, but it's often possible to find a working food replicator in a restaurant or apartment that will dispense nutritious goodies in exchange for garbage, and the water recycling network is generally the last thing to go, so you can usually get water out of any tap and flush any toilet without trouble. Sometimes you get lucky and find a working replicator of another type, and you can have a steady supply of clothing or furniture or industrial equipment until you run out of debris to feed into the hopper.

Some areas are less straightforwardly habitable than those. Millions of miles of magnetic rail corridors for high-speed trains, initially pressure-sealed and maintained at a vacuum but now sometimes broken open and stealing the air from adjoining habitable zones; vast networks of energy transfer lines, insulated superconductor cables weaving around the mag-rail tunnels or collecting into arterial braids as wide as several city blocks, plugging into the cities and naturescapes to power their remaining systems. The innermost levels are full of machinery devoted to the collection, amplification, and distribution of power; the outermost levels are mostly transport infrastructure for moving people and cargo to and from the airlocks in the outer skin.

And then there are the places where either nothing was built to begin with, or time and demonic activity have worn it all away: vast empty caverns crisscrossed with nearly indestructible support struts, sometimes filled with air, sometimes only vacuum. (Areas that are meant to stay pressurized have air-producing replicators that kick in when the pressure drops below threshold and work well enough to stand up to a few small or medium-sized leaks, so in the long run any crack in the seal between a vacuum zone and an air zone will lead to the vacuum zone filling with air. The skin of the shell is self-repairing, so any leaks out into space will eventually close.)

The shell's outer skin has airlocks placed densely enough that a ship approaching from any angle will have several to choose from even now that half of them are broken. Functioning airlocks will require some technical expertise to open, and broken ones will require even more technical expertise to repair, but both tasks are possible for a visitor with no local training to accomplish. Which is handy since no one has had any local training in centuries.

All the habitable areas run on a single timekeeping system, and the lighting in any urban zone's public spaces will dim and brighten on the same 24-hour cycle. Naturespaces may be set to vary their lighting and climate according to individually customized calendars, but even there a 24-hour day is preferred. The standard calendar is 360 days long, with twelve months of thirty days each, because you guys I'm so tired of coming up with interesting calendars.


And... I think that's it? If there's anything else interesting to say about this setting, I can't remember it.