This is an AU of Battlestar Galactica. A few things changed from the series the first is that the Pegasus survived the battle of new Caprica but both Galactica and Pegasus got more battle damage but they also took out all the basestars so they managed to salvage from new Caprica. The next major part of the AU is that the rebel Cylons didn't trust the One's enough to fall for this trap and as such they manage to capture the Hub as well as having 7 Basestars instead of one. But they still loosed the Colony to One's faction and as such where unable to build more ships but they now controlled resurrection meaning that all of the final five are still alive and with the fleet. The battle of the colony still took place as One's faction captured Hera in an attempted to recreate resurrection for themselves as they where disconnected from the hub. The battle was more extreme with the rebels sending 4 Basestars with the Galactica( Pegasus staying with the fleet along with 3 Basestars for protection of the fleet and the hub which the Cylons have confirmed that they can add the Colonials on when they have enough time) with 2 being destroyed and 1 being made irreparable. The Galactica also being made unable to make another jump but they do find earth. Only it's an earth at our predicted level in 2050(which is also the year there). About 98 years till the cannon finding of the Prothean ruins and 107 years till the first contact war. This means advanced tech compared with now but I'm not going to take any liberties with tech only things currently being developed or that have been but are to costly to be made large scale. that means even thou a plasma weapon was in development that since it's been canceled we'd not have one but lasers and coil/railguns are fine as we still putting resource into them and have version of them complete. Also to put ship sizes into perception in the mass effect universe all sizes are based on lenght frigates are 100 meters to 300 meters cruisers are 400 meters to 800 meters anything 800 meters and up are dreadnoughts with 1000 meters the norm and the largest dreadnought made by the citadel races being the Asari's destiny ascension at 1600 meters with the reapers being 2000 meters . Though all dreadnoughts and cruisers in mass effect have 80% of their length made up by the primary spiral mass accelerator main weapon bar the reapers. The Mercury class battlestars are 1789 meters(for the purpose of the story 1800 meters) the Galactica type being 1438 meters(for purpose of the story 1450 meters) and the Valkyrie type being 700 meters. Basestars are 1550 meters but are mostly empty space and out massed by the colonial counter parts along with the Battlestars being very much better then Basestars in pretty much everyway bar fighter carrying capacity at 200 vipers and 50 raptors to 450 raiders and 75 heavy raiders and the Cylons have better missiles but the flak and ECM of the Battlestars making that point not really matter. Along with the fact that vipers and raptors are better combat craft then their Cylon counter parts. Also I got the idea for this story from Brian1972's Organic toasters which is a great story that I recommend. but I stayed closer to the series. Also Thylium is just Oil in this. Feel free to take this story idea just credit myself if you take most for this story or even loosely like I have with the premise of those from the BSG universe finding an earth with no Prothean ruin's detaining the tech evolution of humanity as such the closeted working Mass Relay (with the Prothean's having shutdown and gene/password locked the rest in an attempt to beat the reapers) to humanity is at Shanxi( the Prothean's having solved the static build up that Mass effect FTL causes meaning the relay were only need for speed). Also I'm going on holiday soon so I will not be working on this for at least 2 weeks

Earth had been on the brink of economic collapse when a strange fleet of ships arrived in orbit... well most of Asia and the Middle East had along with Russia with China falling to civil war. after western company's pulled out of China to afraid to end up like Apple or many other western company's with their intellectual property stolen and their money loosed in an unstable economy along with it being cheaper to operate in high tech nations with robotic labor. Which of course lead to a massive loss of job's combined with a people sick of being oppressed and with "loss" weapons from nearby nations finding their way into the hands of rebel groups leading to full on civil war which the rebels won at great loss with China going from about 1.4 billion people to 800 million over the span of ten years from 2023 to 2033 leaving much of the country devastated even with international aid.

For the Middle East it's problems with terrorist groups and the loss of it's Oil revenue in 2040 when the EU, US and the Common wealth nations (Canada, UK, New Zealand, Australia and Ireland form in 2025) switch over to nuclear fusion and thorium salt base fission breeder reactors along with other green energy solutions with graphene super capacitors replacing batters as back up power along with bio plastics ,electric cars and appliances replacing any need for petrolatum. Making the world's largest consumers of fossil fuels no longer buying them. Crashing the market tanking any country's who's income relied on their export.

Russia had major problems in the 2020's blinking on war with NATO. and being sanction left and right which started a new cold war with NATO as neither really wanted an actual war that likely turn nuclear. It didn't last long until it collapsed just like the soviet union before it making the same mistakes in trying to out do the western world on research with a weaker economy and less educate. lucky Russia was stabilized by economic aid. But it still amassed a massive amount of debt. Which it had mostly paid off by the time the fleet arrived but still left Russia technology behind western nations but with the closer ties that the new government had with NATO nations they had they still welded a lot of power. Though they no longer had any power over the UN but that was more because the UN had been disbanded as ineffective especially with two of it's permeant members collapsing.

When the fleet arrived both were shocked with the combined rebel Cylon/Colonial fleet having knowing that the human species was meant to have only 13 tribes not 14 and the people of earth not having know that their was any other humans. However testing showed that humans on earth had genetic drift of around 50 000 years to both Cylons and Colonial's. It was not knowing how this came to be and even though neither know it but testing Asari, Quarian or Batarian and you get some similar results with evidence of genetic tampering 50 000 years ago as well. But they didn't. Neither having access to Prothean data to the experiment in biology they were conduction with Kobol and Earth as the control group's with how similar the world's were they were bound to end up very similar to each other. None the less both came to the same conclusion that it's impossible for what had occurred to happen natural. And with that the idea that alien live is out their and with no idea if it's hostile or not. the nations of Earth along with the rebel Cylon/Colonial remnant. Combine into one calling themselves the System Alliance. The idea of immortally though Cylon resurrection quickly over took humanity especially those from Earth who had largely became Atheist with better education and didn't have bad experience with Cylons as well as the moves toward that with nerve gear virtue reality head set that has to fully scan the brain and download data directly to it. Whereas with the Colonials it was more about never having to fear being wiped out.

It took 20 years to full integrate all the tech bases together. As well as form the new government. But it was impressive. Most of the ship designs in use for space where scraped with only the best let though and even then they were redesign to include all the best tech. Of the combined tech base. The Galactica Class Battlestar called so after the Battlestar that safe guarded the Colonial's for most of the journey that brought them to Earth as well as lead the rescue of the first born Cylon child. Based mostly on the Mercury class but with the middle fill out the match the width of the alligator head with the gap in the head being covered along with the spaces between the engines as well with 5 more primary gun's on each side in the groves and 20 each on the top and bottom arranged in groups of 4 like on the old Columbia class that the Galactica was apart of making 64 primary dual gun's total with the primary gun now coil rail's the point defense (1400 dual guns) uses the same method as do the missile launchers(32 quad launchers) in fact all guns use this method as it's very powerful and need no ejection port(uses both the railgun method and coil gun with 8 rail's in each barrel circling the projectile with a coil behind the rail's to increase speed strength of both method weakness of neither but more power intensive then either alone but still less so then lasers longer ranged as well lasers are on every weapon of this type but are only used when out of ammo or at close range lasers are in the high UV range but are normally mixed with visible light unless in stealth mode). This was to give full gun coverage. Onboard the it contained a resurrection core with body's being build by 3D printing to the exacted make up of the original body when combined Cylon body mods aka nanites and new carbon computing pathway's to aloud the mind's to be send via quantum entanglement to the nearest core. Which is also how the new com's system works. along with everything else the ship water storage Carrying hydroponics bay's with genetically engineered plants to provide all food needed as well as organic material need for organic ink for the ship and even the 6 escorts each has. Refinery to prepare inorganic material. 4 mining ships one in each flight deck to harvest material's and water to feed the massive 3D printers able to make any part the ship needed as well as any item smaller then 4 raptor's put together. 80 viper launch bay's with 240 viper's mk 8's and 50 raptors mk 3's. And ECM with Cylon computers and centurion marines along with a fusion reactor(which has been enhanced with the artificial gravity of the cylon/colonial's which all their ships carry) with graphene super capacitors back up for power at 1.8 kilometers for each Battlestar Galactica class and standard layer armor plate(nano clock(hiding from the EM spectrum when power which takes a lot of from the reactor, adaptive camo, heat masking and sound masking from within) to nano steel to nano diamond to layer graphene to nano diamond to nano steel with nanites layered in to it to repair damage) and military style Cylon FTL (two to four drives in this case four)

The escorts to each Galactica class are 6 Ares class Battlestars which is two Valkyrie classes join on the bottoms with viper launch tubes to the sides with 12 on each side for a total of 24. Each carrying 60 vipers mk 8 and 20 raptors mk 3 with one mining ship. Resurrection core, Water storage, their own hydroponics bay, small refinery and 3D printers able to make anything smaller then two vipers put together, ECM, Cylon tech com's and computers with centurion, new coil rail's weapons tech, standard layer armor plate, military style Cylon FTL(two to four drives in this case two) and fusion reactor with graphene super capacitor back up with a 700 meter size

The new viper mk 8 is just the mk 7 with the new armor, weapon system, reactor system and raider computer system along with the a jump drive added to the viper the same can be said for the raptor mk 3 as it's the same as the old battle raptor's but with the new combined tech and fusion reactor and both used the better and smaller CO2 scrubbers of the Cylons. The centurions have resurrection added along with a voice box the new armor system and coil rail's build gun to replace the old machine gun along with micro missiles. They can also make their own ammo but if they run out their likely just to switch to laser mode(they wanted to included movement thrusters but they where to heavy)

Body armor for people is the talos personal armor system mk 2 that covers the whole body in armor plate with an integrated exoskeleton and movement thrusters(like in titan fall) but the long googles are replace with a normal flat screen with a HUD and all current vision modes with the new standard layer armor plate system as well as an integrated CO2 scrubber and all. The new weapons with the standard armor plate are the FN P90 (range 1200 yard's select fire)and the FN Five-Seven(range 500 yard's semi-auto) with the firing systems now coil rail's . Magazines carry enough charge to empty the number of bullets in them 3 times over as well as charge the gun's capacitors. With the ejection ports removed dust and mud are less likely to get in. Along with a new sight that has variable magnification of up to 10x tracking point and all current vision modes. With a flash light on each's rail system. The Five-Seven's also carrying the laser in the flashlight with the P90 having an integrated lasers system and adjustable carrying strap for the P90. Both also have attachable silencers .

Patrol's are one Galactica class with it's escorts. a Battlestar group is 5 Galactica classes with their escorts. Every planet that has a settlement has at least a Battlestar group with any group settled planet having at least 5 groups to 10 groups as well as any ship yard's ( that are based on the Colony but with all the new technology integrated into it's systems including resurrection cores and 3D printers larger enough to make Galactica classes and the parts to make new ship yard's). Earth itself has 20 Battlestar group's and have just moved to colonized a world named Shanxi and found a strange large metal device s found in parts of their territory but with it the only working example that they found.

The device being studied was very confusing with a strange dark matter reading and a constantly shifting mass. Then one day the device start's pulsing and a fleet of strange ships giving off similar reading to the device came though to be meet with Battlestar group 79. And this. This is where our story really start's.

Sorry that most of this is just tech details but it need to be done I've not decide what fleet it is they are encountering. I have taking so liberty's with what some tech can do but all of it exist even if not able to do what I've listed them as able to do