Multiple interpretations of Hell exist.
Human souls are real and trading yours makes you a worse person.
Contact with Hell and its derivatives changes people.
The Devil is a singular entity and the only one who can trade for your soul.
Mundane weaponry works on the forces of hell.
NO:
Non-Hell supernatural elements.
Afterlife confirmations.
God to counterbalance the devil.
The First Portals Open (Light)
This is the divergence point from history, when the first physical connections between Hell and Earth occur, and all kinds of craziness hits the fan.The first portal opens in just-conquered Constantinople; The Basalt Towers attack the Ottoman forces through it. (Dark)
Mehmed II's victory celebration is interrupted as a vast jagged shimmering rent in space opens beneath the Hagia Sophia, swallowing the great church whole, along with some of it's surrounds. President Botis of the Basalt Towers region of Hell (into which the portal opens) directs his household guard (black-armored giant-mosquito-riders) to investigate in force. Religious terror allows the demons to wreak disproportionate havoc among the Ottoman forces, but they are simply too few to do more than raid, and return to their master to report. The event is Dark because of the fear involved and the precedent of hostility set.Containment zones around hellgates are established (Light)
Noticing the warping influence of hellgates, the governments establish city-wide quarantine zones, which leads to mass civic unrest, but limits the corruption.
How did the person who would become the first immortal meet the Devil? (Dark)
It is night. A pair of Ottoman soldiers walk around the ruined walls of Constantinople, distracted in conversation. As they pass, a small figure, a girl maybe ten years old with an ominous buboe on her neck and dressed in sackcloth, darts behind them, and starts scrambling over a pile of rubble that marks a breach in the wall. The soldiers hear the tumbling stone fragments she dislodges, and yell at her to stop before jogging over, but she has cleared the summit and is gone by the time they arrive.
She wanders the streets, picking through the ruins, finding little. Picking up a discarded musket to use as a walking stick, she draws ever closer to the eerie glow that marks the Constantinople portal, if only because it is the best-lit part of the city. At first, she throws a few loose chunks of rubble into the shimmering thing, but when nothing results, she gets closer and pokes at it with her musket. The portal's jagged edges shift, and one fissure runs beneath her foot. She falls.
She lands on the black-visored face of a Mosquito Knight, who was drawn by the thrown stones. It peels her struggling body from his helm and carries her by one ankle to the audience cavern of President Botis. Botis, in the form of a hideous viper, questions the prisoner, but when it becomes clear that she knows nothing of value, he quickly loses interest. 'Send her with the tribute wagons,' he says. 'Perhaps our overlord will find this novelty amusing.'The First Colonies Form (Dark)
Wars between the various nations of Hell and Earth result in several chunks of territory in each realm being held by forces from the other, depending on who prevailed in the conflict, but most are unstably held, and back-and-forth is common. Consolidating and expanding these areas consumes a lot of effort.
How Did The First Immortal Escape From Hell? (Light)
Eleven attempts, and eleven should-have-been-fatal punishments. How long she had been an enforced guest in the Devil's house, Melania once-of-Achyraus, the First Immortal, did not know. But it ended today, if days had any meaning here.
This time, nothing had been left to chance. The Devil's various vassals mostly hated their overlord, and their envoys had been paid with information she'd stolen from the vast revenue records in Its vaults; those whose tribute rates were lightest had revealed Its secret allies, given the aristocracy of the hells a leverage they'd never had before. In exchange, they had bribed, diverted, waylaid, and disabled the security around the Blade of Light. They thought she meant to attempt an assassination of their overlord, a plan they all approved of, but dared not attempt themselves.
Instead, as Melania's fingers closed around the emerald hilt, she invoked the strangely-formed weapon's greatest power. She had seen the Devil use it to travel between Hells without using the common portals, to visit Its retainers by surprise, and she had heard the incantation It used to do so, for It had no caution against the ears of such a lowly subject. And so Melania spoke the words and cut the air, feeling something within her slice and part as well. She never remembered the memory she paid for that passage, the moment of forgiving her father for beating her for laziness.
She emerged into air that tasted so clean that she gagged in unfamiliarity. The Devil's home knew many forms and flavors, and the air was different in each, but though some of those vapors were sour and some were sweet, none of them were clean. The landscape seemed strange, but she supposed that she had spent more years in Hell than she ever had on Earth, and that was only to be expected.
A sharp blow to her skull felled her. 'Wait,' she cried, 'I've come from Hell, I know... so much about their lords and ways... I can tell you...' A second blow silenced her.
'<What was that foreigner's babble?>' asked the ashigaru who had staved in her head with the butt of his yari.
'<It was babble to me,>' said his companion. He stooped to retrieve the Sword from where it had fallen. '<But I know a treasure when I see it. Leave her for the birds and let's get this to Lord Mōri Okimoto. I bet we'll get a fat reward for it.>'The False Monarchy of Demons (Light)
European demonologists in the Livre des Esperitz/De praestigiis daemonum/Lemegeton tradition are taught how to offer a soul on lease, and influence the RCC into redefining Purgatory.
How Did King John III of Poland Save Europe at the Siege of Vienna? (Light)
The field was strewn with bodies, Croats and Poles and Austrians and mercenary German landsknechts all lying together: some in lines where they had died standing, some strewn where they had broken and been chased down. The groans of the wounded echoed horribly across the field amidst the lingering powder smoke like a scene from one of those Bosch engravings from last century.
A medical party, stumbling from wounded to wounded and avoiding the pools of demonic ichor, were the ones that found her. Even exhausted, shivering and suffering the aftereffects of hexes, she was lucid enough to demand to be brought before the King.
"You're a fool," were the first words he said to her. "You're too valuable to risk your life on these sorts of ventures. That's what we have soldiers for. We can afford to lose them but not you."
She sipped the hot broth gratefully and raised her eyebrows at him. "I recall you risking your life too."
"I'm the king," said John Sobieski. "That's what kings are for. You're our advisor. Please, in future, do what the rest of my advisors do and stay away from trouble. What would have happened had we lost?"
"We didn't lose, though, did we?"
Despite himself, he grinned, and the grin spread to the other lords and the Winged Lancers about him. "No, we didn't. We won. We paid the price but your plan worked and we won."
"So now what?"
Sobieski stood up slowly, his body aching from the fatigue of wearing armour all day, and walked over to the map. "We send messages to King Louis and to the Mohammedans. We find out how they did. And then, unless one of them lost, we can start the real business."
For a moment this placated her; then she realised what he meant and looked up in alarm, spilling her broth. "No. I warned you. I warned you not to do this. It's more dangerous than you can imagine. Defending earth is the important thing."
He grunted dismissively, his huge hands gripping the map table. "I didn't march from Warsaw to Vienna to defend myself or to be safe. Louis and Mustafa can stay and guard the home front like women if they wish. We still have strength enough to march on hell, and while we have that strength we will use it."
The smell of sulphur, both from hellfire and from gunpowder, lingered on the camp all night. She spent that night recuperating in her tent; but as soon as dawn came she stole a horse from a Hungarian huszar unit and rode away unnoticed from the camp of the last Crusader king.
The First Great Exodus (Light)
At the start of this period the corruption of hellgates became obvious and unbearable. The area around them is practically dead - no plant can grow within a kilometer from them, no beast wanders close. Swiss scientists and alchemists develop new technology that stops the spread of corruption and, as a side effect, stops all solid or liquid matter from passing. The cities whithin which the gates are located are surrounded with those perimeters, and their population is exiled into hell, to prevent the spread of corruption.
The period is light, because the immediate danger of hellgates is prevented, albeit with heavy cost.
Perimeter is Invented
Swiss laboratory invents a Perimeter - the network of towers that can create a force field that stops the hell's corrupting influence and non-gaseous matter. The field takes gigantic ammounts of energy to sustain, although later a cheaper variant is invented, that can partialy use hell's ambient fields. The event is light, because a technological breakthrough is achieved.The Amnesty of Lucerne
Refugees from hellgate-infested cities whom fled before borders were closed flock to the shores of Lake Lucerne. The neighboring forest cantons have adopted a massive repatriation effort, and issued a public proclamation asserting the rights of the infernally afflicted. The massive influx of people coping with various amounts of Corruption soon leads local scholars to consolidate their efforts and form the Hölleidgenossenschaft, outwardly dedicated to ameliorating the worst effects of hell's influence, yet privately experimenting on weaponizing Taint.What Price Perimeter (Dark)
Amateur spies seeking to steal the secrets of the Perimeter discover that the taint effects aren't truly blocked – only diverted into living 'sponges,' mostly animals of little value, which become so warped as to be unrecognizable monsters. Disposal of the creatures proved to be hazardous, so when they became too warped for their restraints, they were released into holding chambers to starve, though often they would feed on one another, allowing a few to survive. Some of the spies attempted to publicize the information, others to blackmail the manufacturers. Authorities who wanted the truth and those who were invested in the cover-up wrestled for years before the facts were finally made public. This Event is Dark for animal cruelty.
The First United Republic of Hell (Dark)
This is the period after the hell colonies have stabilised enough that most of their inhabitants are born locally rather than immigrants or exiled criminals, but before the technology to create artificial hellgates becomes widespread. Secessionary wars by individual hells occur, as do attempts to create the titular unified multi-hell settler state. The mood is one of tragedy, as the heady idealism of the late Enlightenment and early Romantic periods becomes muddied with the brutal realities of infernal settlement and revolutionary ideology, and the often shocking tactics to which both earth and hells are willing to sink. It is therefore Dark.The First Immortal's Descent (Dark)
A diplomatic envoy to the Hells of Mesopotamia is waylaid by Shedim separatists. Serving as the envoy's guard, The First Immortal is taken hostage as the only survivor, to be held in the heart of Kurnugi beneath the seven gates of the Anunnaki. As a result, her presence and reasoned approach is sorely missed at the 13th Infernal Congress.
The Last Portals Close (Dark)
Only a relative few portals remain open at the start of this Period, and by the end they are all gone.The Pain Engine is Destroyed (Dark)
While the revolution spreads around the world, a small group of fanatical Purists slips into the catacombs below Paris. Despite the many traps and guardians, they succeed in locating the Blade of Light and withdraw it from the focusing circles. Without the Blade as its power source, the Pain Engine slows to a halt and one by one the minor demons bound throughout Europe cease their labours. The Antipope's reign begins to crumble.Viva La Revolution! (light)
Mehmed XXII's victory celebration is interrupted, as a vast jagged hole opens in the obsidian wall of the Thrice Victorious Palace. A small figure in shining armor and with the blade of light passes through. Hordes of demons and men can be now be seen on the streets, as the old natives of both worlds rebel against the corrupt colonies. A day later, the city finally grows quiet. The first colony of many is cleansed from humans turned demons.