It's said that if you want things done right then you'll have to do it yourself and so here I am, I am greatly dissatisfied at a lot of the halo FanFics out there.
Now on to the next matter
Noble 6 being raised as a Spartan will naturally be quite smart as in my story he'll try to make a slipspace drive to return home.
Spartan 084 Fhajad who despite not making the cut into a Spartan still became a scientists who research slipspace, this is a testament to how smart Spartans are as even if they're not assigned to a non-combat role they can still perform quite outstandingly.
So a Spartan can very well understand a slipspace drive, to them a slipspace drive is like a car engine to an engineer.
--story start--
Spartan B312 or otherwise known as Noble 6 is adrift in space, behind him lays a vast void of space.
Spartan B312 watches the vast starry sky lays bare before his eyes as he aimlessly drift across space.
How did he end up here you may ask?
So Jorge throw him off the covenant ship as he'll personally set off the slipspace bomb, problem is that Jorge activated the bomb too soon and B312 was also caught in the slipspace rupture.
Naturally this isn't the end of it as soon B312 discovered that he's still alive and drifting in space.
At first B312 is confused as he has expected himself to be atomised already by the uncontrolled implosion of a slipspace portal with his entrails being scattered across a dozen light years.
Obviously that didn't happen as he's totally fine for now although the oxygen in his suit can sustain him indefinitely but for now he's safe.
Fortunately for him though he's being attracted to a gravity well of a planet so he won't be drifting in space forever until his suit runs out of oxygen.
There is a bad news though and that the planet he's being attracted is not Reach, he knows this by the sheer fact that geography looks completely different and that his coms are not picking up any UNSC chatter.
As Reach was being invaded you would naturally expect that there would be a lot of coms traffic going around but right now his suit is detecting zero coms traffic.
So it would seem that the slipspace bomb have somehow teleported him to another location.
Much later
B312 slowly enters the atmosphere of the planet as his shields dissipates most of the air friction from re-entry.
It didn't take long before he finally crash lands.
Boooommmmbbbbb
His impact was quite powerful as half a ton of augmented encased in hyper advanced armour travelling at re-entry speed is no laughing matter.
His impact his powerful enough to form a crater, miraculously he somehow survives in one piece.
'Barely even noticed it' B312 jokingly thought as he picks himself up from the crater and heads off.
Awhile Later
Spartan B312 is currently heading to the source of odd communications chatter.
'It should be just over this hill' he thought as he walks up the highest point of the hill but as he does so an unfamiliar city slowly falls into his sights.
'What the...' B312 quickly runs through all the UNSC/UEG coms channels hopeful that he has finally returned to civilisation but unfortunately for him all the known UNSC/UEG channels are silent and there's only this weird coms coms traffic coming from this area.
The signals from this place is not encoded in any format he knows.
Spartan B312 stares at the city from the distance, carefully observes the city architecture trying to make out where he was, but he wasn't able to make out anything familiar.
B312 frowns as he decided to heads closer to examine the place.
A Bit Later
B312 enters the periphery of the unknown city and he is finally able to make out familiar forms.
'Humans?' B312 wondered as he stares at the human looking creatures from behind some cover.
As he looks on it an idea starts coming together in B312's mind.
'Unknown architecture, Unknown coms encryption (nonstandard UNSC/UEG) and Humans... The Insurrection' B312 thought as he suspects that he has landed in an insurrection controlled planet.
'Looks like here my next mission' B312 thought as he looks at the non-UEG affiliated city before him.
Months Later
After months of infiltrating, information gathering, dozens of missing persons later
' I think this is much more complicated than I had initially thought' B312 thought as he finally starts believing that the slipspace bomb might have transported him further than he had initially thought.
After finding a safe hideout and B312 was quite baffled by the information he has gathered from the "insurrectionist"
At first he had thought that the "innies" were quite tight lipped or playing the fool when he was interrogating them about the UNSC and the UEG but after around a dozen more people later, he starting to have doubts.
Then he had thought that perhaps this is an elaborate brainwashing scheme devised by the "Innies", perhaps if they had destroyed all records of the UNSC and the UEG then perhaps a few generations later they won't even realised that they're just a bunch of breakaway rebels terrorist.
In the process of kidnapping these people however he did manage to get his hands on some Omni-tool.
Strange devices with multiple uses, one of those is getting access to the Extranet. There he has been able to gain a lot of information.
The System Alliance, Citadel, Asari, mass relays , Element Zero and so on.
After absorbing all this info brings us to the current predicament.
' I think this is much more complicated than I had initially thought' B312 thought as he finally starts believing that the slipspace bomb might have transported him further than he had initially thought.
Yes much much further as than he had initially thought as he's in a completely new Galaxy, the one next to his previous one actually.
As for how there are humans in this galaxy? B312 will never know.
(For lore explanation it could ether be forerunners or precursors, take your pick as this won't be a major plot point in this story. It will just be there are humans in Mass Effect that are genetically similar to the point that they're undistinguishable form those in Halo galaxy.)
B312 found this as he saw a bunch a of familiar galaxies while reading some astronomical reports. he did further research and found more pictures if other galaxies, using the various markers that these galaxies had B312 is able to find the orientational different for those in his memory and is able to triangulate his home galaxy'a location.
Fortunately it's still within the local group which is the closest another galaxy can be in universal terms, the bad news is that even though it's a galaxy next to his current one, the distance between galaxies are vastly larger than the one between systems.
It would take hundreds of years just to with the fastest slipspace drive just to attempt get to the closest one.
After reviewing the information in the Extranet Spartan B312 was very dissatisfied with how the System Alliance does things, to bend the knee to to a bunch of alien aggressors was completely unthinkable to him.
The Turians invaded a human colony unprovoked and the next thing you know the System Alliance is signing treaties of limiting arms, while joining the citadel which one of the heads is lead by the Turians, the ones who invaded them.
The list goes on but B312 doesn't really view the System Alliance in any bright light as any UNSC personnel would fight for a planet till the last man! They will fight even as rays of concentrated beams of plasma rains down on them! They will fight with rocks and sticks if they have too!
Anyways B312 primary interest is heading back to his home galaxy, but how?
Well the first thing is acquiring a ship, but here in lies the next problem FTL in this galaxy aren't really meant to travel vast distances, they use Mass Relays for that.
And last time he check they don't have Mass Relays that can travel intergalactic distances he'll need a slipspace drive for that, but as you know they don't have slipspace drive in this galaxy.
So he'll have to build a slipspace drive, it's tall order sure but far from impossible, slipspace drives has been around for hundreds of years now, not to mention during the course of his training as a Spartan he eventually came across the theory how slipspace works and how to fix a damaged slipspace drive.
He knows the Theory and he knows it's internal workings so he should be able to build one right?
While it won't be easy and would require a vast amount of resources but it sure as hell beats getting stranded on this alien loving galaxy.