Disclaimer: the information related herein is a summation of IW's lore based in part on cards, previous dev statements, and previous iterations of the campaign. I'm not LM, so I don't know if any of this is still accurate, but I'm trying to stay as true to form as possible. Various others have put forward lore summaries before (CthuluGirl's comes to mind, but is no longer available since the Infinite-Network is down). And, as an added bonus, I will not only be retelling the lore, but I will throwing in jokes every now and then, such as Aberion's Life Goals. Without further ado, let us begin!
A long time ago in a galaxy far, far, away
Once upon a time there was a universe. It was incredibly nice. And there was this chick named Aleta. For whatever reason, the universe blew up into smithereens, creating a multiverse. Aleta's personality was likewise split into a smithereen amount of pieces, and there ended up being one immortal version of her for each resulting dimension.
The New Layout of the Multiverse
The best imagery I can come up with for this is that of a fishstick sandwich. You have the top bun (Solace), the bottom bun (Torment), and the fishsticks, which are the different dimensions of the multiverse based off of the original universe. These fishsticks are lined up side-by-side in a chain, with each one bordering its neighbor, in the following order: Talich--Untamed World--Avarrach--Reisch. There are some inconsistencies here in terms of cards and lore (for instance, Coyle goes from the Untamed World to Reisch, seemingly skipping over the dimension that was positively overflowing with undead, and the entire existence of Pras is more or less non-canon), but this is the generally accepted structure of the multiverse.
The Origins of the Sleepers
Avarrach was a pretty swell place. Super advanced tech made everybody's lives easy. Only problem is that there's this one guy who was in love with Aleta, and since she was immortal he was kinda worried about that being a problem in their relationship, so he designed these nanobots that would render you functionally immortal by repairing any damage to your body and dealing with any symptoms of aging. As an unfortunate side-effect, the nanobots decided that living was a problem and inadvertently killed everybody on Avarrach whilst "fixing" them of that pesky mortality problem. Aleta, being immortal, was rendered insane by having to constantly fight off the nanobots--she healed naturally, after all, so her existence was a painful struggle between the Virus trying to rebuild her as a machine and her own immortal physiology trying to reassert itself and rebuild her as a biological. Once everyone was fixed by the virus except for Aleta, it ended up going dormant because there was no-one left to help.
The Talich Storyline
So the Flame Dawn set about conquering the world using weapons that they purchased from Genesis Industries. Having done so, Aberion woke up one morning and looked at his life goals:
1) Find a really cool hammer
2) Grow out hair
3) Form a cult of personality around oneself
4) Form an empire based on that cult of personality
5) Conquer the world.
So Aberion was drinking his morning coffee, going over the list in his mind, checking off the boxes one by one, ah yes, very successful, when he remembered all of a sudden that technically he only ruled some 90% of the world. Genesis Industries still held onto the remainder. And he scowled and was wroth with wrath.
In a previous iteration of the campaign/tutorial, an expedition by Nyssa strays onto FD territory and gets promptly attacked. This is followed by a FD assault on a position held by Lucca (who, obviously, survives this attack) and a declaration of war between FD and GI. This war starts to get off the ground when suddenly KABLAMO! a rift to the Untamed World/Old World opens up and out spill some beasts of the Warpath.
Seeing a prime opportunity to conquer some random place, Aberion allies with Genesis and launches an invasion of the Untamed World. This is met with mixed success until suddenly the Sleepers arrive through rifts between the Old World and Avarrach. They're terrifying. The GI and FD promptly ally with the WP in order to fight off this menace, but it just doesn't work. Abandoning the WP to its fate, the Talich Expeditionary Force (as I call it) does its best to keep the zomborgs out of Talich. Bromich puts on a jetpack and dies fighting a cyber infested dragon (unless, of course, you used a well-timed exhaust), and the forces are reduced to a breaking point. At this time the Prophet Karani of the WP opens up a portal to Solace, aka Heaven, and the Overseers spilled forth to deal out some sweet sweet justice on those zombies with some cool-looking guns and tron lines.
The Reisch Storyline
One day on Reisch, Aleta the Immortal Sorceress was considering her list of life goals:
1) Find a really cool staff and cloak
2) Grow out hair
3) Form a cult of personality around oneself
4) Capture extremely powerful demons for use as hamsters
5) Laugh maniacally in the face of the EPA and OSHA
6) Conquer the world
Just like Aberion, Aleta found herself unable to check off the world conquest objective. She had already captured Vasir, a stupidly powerful demon (hereafter referred to as an arch-demon) from Torment (aka Hell), dumped loads of magical waste/fallout on the countryside in flagrant disregard of environmental safety protocols, and banned safety railings from Verorian architecture, but she just couldn't beat the Descendants of the Dragons. To make matters even worse, that failure to properly dispose of toxic waste had corrupted various people into the Exiles, who were roaming around chipping away at her authority aided by another arch-demon from Torment, Nysrugh. The DoD, led by their sages and Ao Shun, were sort of watching this and making sure that at least their turf wasn't a wasteland of pollution while doing their best to keep everybody else outside the walls. When the Sleepers came through, they wrought some serious havoc. The Exiles were already too crazy and disorganized to fight back. The Cult of Verore was too unstable to hold them off. And even the DoD struggled to keep those zombies off of their lawn.
The disaster for the Cult of Verore reached its height when Vasir broke free of his bonds, chained Aleta inside a hamsterball, and wrecked the Lone Keep. After that the CoV broke down into internal powerstruggles, only saved from total annihilation by the destruction of the Sleepers by the Overseers and the already less-than-optimally-organized Exiles. Meanwhile, the DoD's wall still stood, albeit in need of a good wash to remove all of the zombie and demon guts.
About those Overseers...
Let's backtrack: the Overseers showed up in the Untamed World and began to purge it with lightcasters. They teamed up with the Flame Dawn and Genesis in this endeavor, ignoring the WP because Angels feed on human emotions, not animal emotions, so it was completely okay that they nuked the Untamed World because there was no loss in food supply, as it were. Talich got cleaned up, the Untamed World got nuked and cleaned up, Avarrach got cleaned up, and eventually Reisch too was swept clean of the Virus (though a certain arch-demon, sworn enemy of the Overseers, made some trouble). The Sleepers have been stopped and eradicated! Awesome! Well, mostly. You see, back before the Overseers showed up Orion noticed that the Talich Aleta was immune to the Virus. He then tasked her with exploring Avarrach and finding out what she could. Aleta found... herself. Not in terms of an identity crisis, but literally. Taking the Immortal Sufferer back to Talich, Orion and Aleta worked on a cure for the Virus. When the Overseers caught wind of this, they were upset. To them, the virus didn't need to be cured, just eradicated. Moreover, it was feared that the GI might weaponize the virus. So the Overseers and FD declared war on Genesis (again). Sol shot Orion, but it is to be noted that Genesis is still holding out. Good for them. They also evidently found a cure for the Virus, as seen on Reborn when the Avarrach Aleta is noticeably virus-free and sane. Booyah!
The other sour note of the Overseers is that they weren't content to save the world and then just leave. Concerned with the existence of the rifts between worlds, the Overseers turn into the TSA and begin policing inter-dimensional traffic, including questioning all involved in the initial travels between worlds. This is a less than popular and incredibly oppressive policy that does not endear the Overseers further to Genesis, the Warpath, or anyone but the Flame Dawn (with Aberion having sold himself out in return for more power and a shiny set of metal wings).
So that's most of the lore up until the present in a nutshell.
But wait! There's more! Who wants to play... what's up with that Agent Coyle?
Ah, the Coyle Lore. This is where conscientious, Lore-minded folk go to die. The Agent Coyle Lore is so convoluted, confusing, and at times contradictory that really the only one who understands it is Coyle himself--and that's on good days. I had general disclaimers above that this isn't official, but I'm gonna add in an extra disclaimer that this entire section is mostly guesswork and trying to patch together an extremely convoluted picture.
Let's start off by talking about Coyle. His particular powers involve absorbing the powers of others and some manner of time-travel. Coyle started out on Talich and absorbed powers from FD and GI. He travelled to the Untamed World and became a Primal Hunter. He then skipped through Avarrach on his way to Reisch and took some lessons from the DoD. As the Sleeper menace became menacing, Coyle realized that he would need some help fighting them off even with his considerable powers. It is then that Alpha One, an earlier, younger, more reckless version of Coyle, jumps through a rift and meets himself. The travelling Coyle lets Alpha One absorb all of his powers, and then good old Alpha One promptly Leeroy Jenkins his way into a horde of Sleepers and becomes a Zomborg. NOTE: This particular line of lore directly contradicts some of the flavor text on Alpha One, but is taken from an old interview with Coyle himself. So... I'm going with it. Now, Good Guy Coyle realizes that he's done messed up and is out of powers to fight the Sleepers, so he sells his soul to the CoV to get some power back while his undead self joins the Exiles for the lulz and evulz and such. Good Guy Coyle then joins up with the Overseers and confronts his demonic/zombie self in an ultimate showdown of ultimate destiny, where they somehow merge into Agent Coyle Divine-Demonic--and this isn't even their final form!
I have no idea how the two newest Coyles, Superior Symbiote and Assimilator, fit into the lore. On the one hand the Sleepers were said to have been completely eradicated by the Overseers. On the other hand LM has had difficulty saying goodbye, and in this case I think they disregarded an already convoluted and messy piece of lore just to print more Sleepers cards.
BONUS: Pras and the Defiant Hermit
These two cards are messed up. In terms of lore, they shouldn't exist. FD has had no canonical contact with the Verore (in spite of some flavor text and campaign missions that are meant for instructional purposes), and the same goes for the Warpath. The suggestion I proposed two years ago was that Pras defected from the FD whilst in the Untamed World, fought his way through Avarrach, and joined up with the CoV for a time. However, my theory goes, he then grew disenchanted with the CoV and with humanity in general, cutting back through Avarrach and finding solitude on the Untamed World as, you guessed it, the Defiant Hermit. Now unlike everything else in this post, this is not and never was at any point in time canonical. However, it does a good job of explaining the existence of those two cards and is a fond memory of my first days in the game and on the forums. So I'm going to hold onto it.
And there you have it: a basic rundown of an approximation of the Lore of IW--or, at the very least, of what it used to be during previous iterations of the campaign.