Darkening

Darkening was a massive slave rebellion that led to an end of the Silinrul Empire, ultimately turning out to be one of the causes of the extinction of the Silinruls as a specie. It was a culmination of long process of entire species being enslaved in an extremely evil fashion by the Silinruls, with the slaves finally gaining ability to strike back when the Silinrul Empire deteriorated following it inhabitants ascendence into machine forms.

The Conflict

Prelude

The machine ascendancy that the Silinruls underwent made them increasingly complacent and, in most cases, broken. What's more, the Ancients expansion started being an increasing threat, slowly pushing the Empire back from the border regions and increasing the mutual dislike between the two species.
Ancients - it is mostly a theory, since there is no conclusive evidence - concocted a special virus that sabotaged the Empire's control over the Shoggoth Plague, a bioengineered weapon of mass destruction that could be used to strip clean every rebelious planets with the defenders unable to do anything. While Empire's hold over their coreworlds was firm, there was a permanent threat from the so called breeding planets, worlds dedicated to hosting not processed parts of the subjugated species, devoid of military technology and expected to breed to replenish losses, punished if the slaves failed to fulfill the quota.
Even Silinruls were afraid of what the Shoggoth Plague could do... at least before they become the living machines. Without their cutting-edge military technology, defending your planet against a rain of bio-matter assimilators was absolutely impossible.
The fear of the Plague - one of the building blocks of the Empire - disappeared when it began obliterating whole planets at random, proving that the Empire no longer controlled it. Just as the forces of the Silinrul Empire scrambled to stop the Plague, a Darkening began, with more and more breeding zones rising against the Silinruls.

Deployment

There was very little organization during the Darkening, with both sides acting seemingly completely at random. The war was waged on a thousand fronts, with local Silinrul Empire commanders attempting to squash local insurgents before they manage to steal and copy enough of technology to become a serious threat. All of that while at least half of the Empire's forces (including most elite formations) were busy fighting gruelling war for attrition against the Plague (and, later, Ancients and the Plague once again).
The lack of central command amongst the Silinrul is curious, but mostly unexplained. According to some theorists, Ancients somehow decapitated the Empire's government in face of chaos, hoping to lead to its ultimate collapse. According to others, central planets of the Empire were scoured clean by the Plague that devoured everything alive, living the machine Silinruls to collapse without any of them knowing how to operate their power plants anymore.

The Engagement

First Phase

First phase of the rebellion was done mostly in conventional way. Planets rose against the Empire and sooner ot later were besieged by local forces of the Silinrul Navy... that, however, lacked ground forces required to reconquer the lost world. After all, the Empire never waged ground warfare, relying on Shoggoth Plague to wipe non-compliant planets from the list of inhabited worlds. Something that was now impossible.
All of that while the most elite navy formations were busy fighting against mutated strain of the Plague that not only began attacking planets on random... but also started evolving. Soon being smart enough to hijack ships and use them to spread to another planets.
This phase ended when the so called Beta strain of Shoggoth Plague was believed eliminated, as the returning navy easily broke the power of few more succesfull rebellions that managed to spread throughout at least several planets. Several planets surrendered.

Second Phase

Second phase of the rebellion happened when a sudden invasion from the Ancients once again broke the Empire, forcing it to redirect big part of its navy to stopping the threat. This caused the rebellion to explode again... and resort to extreme measures.
First phase events proved that trying to wage conventional war against the Empire was a suicide. Even in its current, barely working form - with 95% of the Silinruls degenerated into mindless hedonists and merely 5% actually trying to keep the Empire afloat - it still possessed almost endless resources and industrial capabilities. Not to mention being massively superior in terms of military technology to even best outfitted rebels. It was going to take at least few dozen of years for any of them to catch up, and before that happened, all planets of the rebels were going to be destroyed.
There was only a single way for the rebels to succeed. The Darkening.
Rebels began purposefully targeting the Empire's means of energy production. They couldn't stand up to enemy technology - so it was time to take it from them. Just as the Empire was busy fighting war against the Ancients, the rebels (once again capable of spaceflight) began raiding their planets. Destroying orbital infrastructure and launching orbital bombardments against any sort of power plants.
The Silinruls planets started going dark. Their expansive infrastructure - created by centuries of unbrindled hedonism - now began being a liability. Bombarded planet had to switch off everything, part by part, sooner or later ending up in a state of civil war against completely degenerated Silinruls that due to breaks in their own programming could no longer think straight and began seeing the energy brownouts as a threat to their life style.
They could only indulge themselves, no longer able to change their minds or accept new informations entirely. Rebels used that against the Empire.
With major power plants destroyed and planets - together with their precious industrial capabilities - taken out of the picture, the rebels began targeting means of producing fuel as a whole (especially mines of radioactive materials etc.), which not only impaired the population of the Empire but also their military. In extreme cases even atmospheres were polluted, to prevent the enemy from using solar energy to supply the remnants of its infrastructure. The Empire was dying, forced to fight against Ancients, rebels and their own broken population.
It is hard to say how long the war was waged, but the rebels were on the brink of victory, with Silinrul Empire almost wiped out, when the third phase started.

Third Phase

Unaware to all participants of the Darkening, the Beta strain of Shoggoth Plague wasn't wiped out completely. What's more, it mutated further. It changed from complete bio-matter devourers into much more picky eaters. One preffering sapient species, whose genes were seen by now actually thinking Plague to be useful in the proccess of self-improvement.
The so called Gamma straing Plague eruption took all participants by surprise, overwhelming what remained of the Silinrul Empire and devouring most of the sapient life in southern part of the Milky Way. Ancients survived and, in fact, probably saved the rest of the Galaxy by sabotaging the Plague's hivemind into a dormant state. The rebels died, and the Silinruls died soon later as the Plague devoured the slaves that kept the remnants of their infrastructure in working condition.

Outcome

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Start Date

BC 5150

Ending Date

BC 5050

Conflict Result

Notable part of intelligent life in Galaxy wiped out.

Belligerents

Ancients

Led by

Strength

Unknown.

Casualties

Unknown.

Objectives

Unknown.

Silinrul Empire

Led by

Strength

Tens of thousands of warships.

Casualties

Silinruls wiped out as a species, Empire destroyed and fleets obliterated.

Objectives

Survival of the Empire.

Rebels

Led by

Strength

Probably hundreds of planets and their entire population. Billions of rebelliants and hundreds of improvised warships.

Casualties

Wiped out to the last.

Objectives

Destruction of Silinrul Empire.

Shoggoth Plague [Beta and Gamma strain]

Led by

Strength

Bioplague capable of scouring the whole planet of life in hours, later on capable also on creating life used to hijack hundreds of ships to use as a means of spread.

Casualties

Beta strain almost wiped out by the Silinruls, the Gamma strain pushed into dormancy by the Ancients, the Hivemind of it presumed to be dead.

Objectives

Consumption of all life in Galaxy (Beta strain) and consumption of all intelligent life (Gamma strain).