Droid Warfare
When the Xylan as a species finally vanished, their technological terrors remained. These A.I.s were loyal to their programing but could think and act in ways atypical of normal droids as they possessed full sentience.
Xylan Weapons:
The main force of the Xylan military was its incredibly fast and powerful navy. These ships became known as the Eternal Fleet as the plan was to have them always on standby even after all life had been wiped out.
Their sizes and power output are simply awe inspiring- at least for the time. To get a sense of the size of the standard warship unit it is best to compare them to more modern warships of comparable power.
Each ship was almost a kilometer long. Each ship had a long and cylindrical body but oddly enough, they had large towers jutting out from the front. These front towers together were nearly equal to the very length of the ship. The reasons for their existence are obscure, but it is likely part of the design to house a large cloaking array. Apparently, a pitch-black cloaking field would surround the ship, but two points at the end would stay outside of the cloaking field to steer it. These sensors had their own cloaking methods, but were still transparent enough to see. Therefore, the bulk of the ship could stay concealed while the tips of these towers provided a large field of vision for each ship. Additionally, most of the ship's weapons were located on the towers. The reason for this being that they were designed to be ambush ships. With most of the armament on the front, they could lay a heavy field of fire before retreating again. The same general principle of maximizing the surface area to weaponry ratio was used on the Hammerhead class cruisers famously used during the Old Republic and Rebellion eras.
The total output of these weapons were roughly equal to the Clone Wars era Victory I class star destroyers. While the output of a Victory I is meger compared to Imperial and even contemporary star destroyers, they are still dangerous warships- especially in comparison with warships during the Hundred Year Darkness. Additionally, unlike the Victory I class star destroyers, they were not designed for heavy ship-to-ship combat. Instead, they were designed for hit and fade attacks- hence their cloaking shields and full frontal assault weaponry.
Perhaps their most deadly weapon was their hyperdrive engines. Each ship had a hyperdrive class rating of (0.6). By comparison, the famous Millenium Falcon had a class of (0.5). Most modern warships have hyperdrive classes no greater than (1.0), but during the Clone Wars the Acclamator class assault ship had a standard hyperdrive rating of (0.75) but with hyperdrive boosters they could accelerate to (0.6). Additionally, ship in the Eternal Fleet was equipped with specialized computers which could calculate the entrance speed and momentum needed to minimize Cronau radiation. As a result, they could slip into a system undetected and wreck havoc before quickly fading away.
The Eternal Fleet's army was mainly used to support the Fleet itself rather than as active agents in combat. The army was composed entirely of almost the same model of droid. These droids were called Skytroopers. They were relatively easy to manufacture with the technology of Iokath. Each droid was equipped with a blaster rifle and a repulsor-pack and steering fins so that it could maneuver in the air. These droids were dropped from specialized dropships where they would then hover down and take control of specific locations on a planet. Very rarely were large scale armies called for as the Eternal Fleet had little reason to launch ground campaigns. However, on the rare occasion that larger operations were required, the fleet would send down walkers to serve as heavy artillery to minimize loss of droids.
One reason that Skytroopers were rarely needed is because once the orbiting planetary defenses were wiped out, the Fleet would blockade the planet with their massive Star Fortresses. These were large space stations designed to prevent things from escaping the planet. They would simply be parked in orbit while their patrol craft would circle the captured world. Skytroopers would occasionally be sent down to put down resistance movements. Their offensive and defensive capacities were not too great, but they usually didn't need to defend the planet as each captured world already had its defenses taken down.
Each Star Fortress was powered by a small hypermatter fusion core. Oddly, this core was open revealing the self sustaining fusion reaction. This was a common design for Xylan fusion reactors. They were very powerful but slightly more unstable than regular fusion reactors. As such, they were often built next to bodies of water so that they could be drowned in the river. Often, the safety mechanism consisted of a sentient eight armed droid that could raise and lower the fusion reaction into the waters to shut it down. However, in space, the plasma was often simply vented. This could be used as an offensive attack. If a large rebellion sprang up on a planet, the Star Fortress could simply rev up its fryers to full power before ejecting the star at the planet. The fusion reaction would continue to be stable for a few minutes as it drifted down before exploding in a fifty megaton blast.
All of these resources would be controlled by the A.I. systems. And if that's not enough, none of these are even the superweapons designed to actually kill all life on each planet. These weapons were often kept in reserve and only used on the most dangerous planets after all defenses fell as the superweapons themselves were designed for destroying planets rather than sustained space warfare.
Superweapons:
The actual superweapons intended to wipe out all life in the galaxy came in many forms, but there were two main types: the gravity weapons and the superlaser weapons.
Gravity based weapons were usually attempts to recreate Celestial Cosmic Turbines. They were very large, sometimes as large as a large moon. They had a large hollow core that contained the equipment needed to focus gravitational waves, but the core also housed a large fusion reactor that powered the continual waves. These waves were then focused on the station's intended target. They could usually destroy a planet in two ways. First, they could fire all stored potential energy at once thus shattering its core. However, this would leave behind a rocky planetoid rather than a field of rubble. A second way would be to pair up with another station and focus on building up pressure in the core by slowly pulling and pushing the planet with gravity. However, while this would cause cataclysmic natural disasters, it was not sufficient to destroy the planet.
A more direct approach was superlaser based weapons. These were often smaller, about the size of a large asteroid. They had used Gravatic Polarization Beams to focus hypermatter into a beam which was sent on a path into the core of a planet. However, these beams were usually not powerful enough to completely destroy a planet, rather they left the surface a molten heap of slag thanks to the powerful volcanic shockwave.
In order to accommodate for these limitations, the Xylan designed a planetary destruction to be a multiple step process. First, the gravitic weapons would orbit the planet building up pressure in the core. Then three to five, or even sometimes seven depending upon the density of the planet, of the superlaser weapons would fire simultaneously. The hypermatter reaction would build up in the core and the planet would be shattered with the shards being flung by the rouge gravity wells in multiple directions. All this done to eliminate any possibility of life coming back. The entire process would be monitored by super intelligent droids.
As can be imagined, this process took an insane amount of energy- far more than fusion alone could provide for. Instead, these reactors used a much more powerful version of the hypermatter fusion model common in their smaller ships. This reactor would fuse hydrogen to create helium, then the helium would be annihilated by the hypermatter reaction. To keep these reactions going, these superweapons would travel with huge teams of harvester droids. These droids would harvest hydrogen from the depths of space to feed the space stations. Additionally, occasional mining colonies would be setup to harvest more massive elements such as Uranium or hyperbarides to seed the hypermatter reaction.
The Solution to All of Life's Problems:
This process was very lengthy. As a result, even if the annihilation got going, it would take a very long time to spread across the entire galaxy. As a result, the plan, ironically dubbed the Solution to All of Life's Problems, was implemented in stages.
In the first stage, the Eternal Fleet would blitz the Galaxy with a series of surprise attacks. Despite their massive technological superiority, numbers, and the raw power of each warship, they could not simply take over the Republic without a long and drawn out fight. Due to the non expansionist nature of the Xylan, the Fleet would have very few resources to replenish destroyed forces. As a result, they would have to perform a series of fast and quick strikes to target the Galaxy's weak points- similar to Pall's Star Forge Strategy. However, it is likely that due to the overall competence and efficiency of the droid commanders, the odds would have been in their favor.
This would be designed to weaken infrastructure and take down all space based defenses. The idea would be to pretend as if they were some type of normal invading force that wanted to rule the Galaxy. Then, when the most dangerous planets were under their control, they would wipe these planets out quickly and efficiently. This would also be in two stages. First, the planet would be quickly fired upon by a superlaser to kill off most of the native population, and only later when the rest of surrounding space is secure would the planet itself be demolished. If this actually happened, it is likely that Coruscant, Alsakan, Anaxes, and other core worlds would be the first to go. Kilometers of steel and permacrete would come crashing down with ash and lava taking their place. This would have been designed to cripple and galactic economy and eliminate the center of government. Without these planets in place, the Galaxy would fall into anarchy.
After this preliminary stage, the droid generals would analyze the data with psychoeconomic principles before planning the next stage. They would then systematically target the strongest centers of government that pop up in the next few years while their superweapons would annihilate planet after planet.
The planets would be destroyed based off their importance. First, the superweapons would be used one at a time on most locations that have a possibility of starting a rebellion that could spread. Then, the most dangerous planets would be picked off one by one. Then, the droids would hunt down and keep following any movements of people who seek to survive the great extinction. Once the entire galaxy was reduced to a pre-spacefaring society, they droids would take their time and eliminate each planet one after the other until no planet can support sentient life.
But they wouldn't stop there. A large force would then be sent to explore possible satellite galaxies to continue the process. The remaining droids would then proceed to annihilate any planet that had life to begin with to prevent it from becoming sentient. After this, they would turn to a lengthy campaign to blast any rock that even had the potential of life into dust all the while looking for anything else to kill. And after a million years, any droid that did not go completely insane, or rather even more completely insane, would look out across an empty and lifeless galaxy.
Needless to say, this is a very long term plan. It is thought that even the first phase of their plan, that is wiping out all major points of sentient life, would take ten thousand years. The droids did have the ability to adapt and construct more weapons and ships using Iokath and other much smaller facilities, and while these would cause the rate of expansion to steadily increase, it wouldn't be an exponential increase unless significantly more facilities were built, and given the level of sophistication of their technology, that would take time.
Why this didn't happen:
The Xylan went extinct sometime between 12,000 and 10,000 BBY, long before the Hundred Year Darkness. It is unknown how the Pius Dea or Jedi controlled Republic would have responded to such an enemy, but that is a question for alternate history novelists. What is known is that the droids had conducted extensive psychological studies on the Galaxy up to this point. It is believed that the sudden and rapid changes in alliances during this era were one of the main reasons why the Eternal Forces held back as they wanted a more complete psychological profile. However, it was this snooping that got them into trouble.
Another race of incredibly advanced sentient droids had taken notice of these investigations. They are known as the Silentium.
The Iokath-Silentium War:
The history of the Silentium, that is where they came from and what did they do, would be far too long to fit here as they have a habit of popping up at the most unexpected times in the midsts of the strangest galactic events. To make a long story short, they are a race of large sentient droids who lurk out in the Unknown Regions. They usually don't get involved with Galactic going ons, and the last time that they came to the attention of the Galaxy at large was during the Hidden War in 50 ABY when they were almost destroyed by Chiss forces. However, while mostly harmless, they don't take kindly to other rouge A.I.s in the Galaxy. For unknown reasons, they grow incredibly hostile around other fully sentient droids and when these droids seem to be multiplying, they step in to annihilate any trace of them.
When the large and technologically advanced Silentium found out about the Eternal Forces and Iokath, they became enraged and attacked. The war was long, brutal, and wore down both species. However, the clear winners were were the Eternal Forces. The Silentium were more than capable of fighting, but they were even less prepared for a long term war than the Eternal Forces were. As a result, they species survived the war but only barely. The only reason that the Eternal Forces didn't pursue them is because their own casualties were heavy as well.
The Eternal Forces were not prepared to attack a race of droids. They had been studying the behavior of organics and as a result when faced with a completely alien droid race, they made several mistakes. To rebuild, Iokath was set to construct new resources to repair their superweapons while the droid A.I.s went dormant. This process continued for thousands of years as the lesser A.I.s and automatons continued to repair. The war itself went unnoticed by the Galaxy at large until historians discovered the remains thousands of years later when they found out just how close the Galaxy had come to annihilation.
This is the state that Tulak Hord found them in when his fleet discovered their remains and awakened them.
