So I plan on running an alternate lore type thing for 40k that I found on 1d4chan, called The Eldar Gambit. The idea is that at the siege of Terra, eldrad makes one final plea to the emperor. No one knows what was said, but when Horus strikes the emperor, the big E uses the sword to travel into the warp briefly and eat slaanesh's stomach, thus freeing the Eldar from She Who Thirsts. As a result, the Imperium and the Eldar are now very closely aligned, with the Eldar being considered a department of the imperium.

Apart from needing some believable lore on how that would change things, what kind of technology would the imperium potentially make since now moving it with Eldar tech is an option?

Honestly? Technology wise properly very little. The Imperium might be allied with a couple of Elder Craftworlds but that doesn't change the fact that the Elder are rather unlikely to share their technology... and the Tech Priests of Mar would make **** sure tech heresy wasn't committed by allowing their tech to become mainstream.

Even in the event that the Emperor did do the Elder a huge favor and freed the souls of the dead elder up to that point, I very much doubt you would have gotten all the Craft worlds to sign up with the Imperium. That would imply that humans are on the same level as the Elder themselves, a fact that will no doubt result in full on civil war between the 'Pure' Elder and the Imperial ones. Not to mention the Dark Elder, who would properly be enraged by the Imperial Elder as well for daring to claim that monkeys are the elder's equals...

Honestly, I don't think it would change much! The Eldar being freed from Slaanesh would still be a shadow of their former selves! While they would no doubt be thankful for their deliverance I doubt that would translate to as close an alliance as has been suggested. The average imperial is too xenophobic and the average Eldar far too arrogant for that!

More likely, I believe that the relationship would become more like it is in WH fantasy: A mutual nonaggression pact with occasional help from either side.

The Dark Eldar represent a wholly different problem: Freed from the curse of Slaanesh, they would have nothing preventing them from establishing permanent colonies outside the webway. From there they would likely seek to carve out an empire of their own!

(I'll assume that despite any improbabilities, the alliance did happen, because game). TLDR better laser & maybe suspensor tech, psykers using Eldar gear, maybe webway access. Harlequins Harlequins Harlequins. (I like Harlequins. )

• Eldar population boom. Still not very big compared to the imperium, but enough growth to need the Maiden worlds for colonization. Maybe a population shift, more Exodite & less Craft or Dark? (either Exodites have more sex, or souls don't want to reincarnate as Dark Eldar)
• Big improvements to psykers. They are the only humans that can use 75% of Eldar tech because that stuff is psychoactive. If it is possible for them to learn the runes, then generally safer, less psyker possession.
• For regular tech, possible improvements to las weaponry. Can Techpriests copy how the Eldar make their lasblasters. or does it require psyker manipulating wraithbone etc? Aside from that, very little change because their tech's have completely different foundations. Maybe Eldar start suspensor factories.
• Webway access. Stabilizing the one under the Golden Can, space marines helping clear out the chaos-infested paths (Demons are like 'these dudes souls don't taste as good as Eldar. Lets leave')
• Harlequin Inquisitors. Without those souls, Slaanesh weakens and they have time to fight Chaos on the human front.

Actually. Look at the eye of terror. All those souls that Slaanesh ate at his birth. Trillions maybe? Those souls would way outnumber Craftworld, Dark, and Exodite combined.

Only War, Deathwatch, Black Crusade games all set inside the webway.

If the Emperor managed to free the souls of the Eldar from Slaanesh, one major difference? Some of the Eldar would have shown up and healed him, so he wouldn't need to be permanently installed upon the Golden Throne.

He's up and walking, and can put the Imperium back together after the battles of the Heresy. No Cult of the God-Emperor. No Ecclesiarchy. Probably no breakup of the Legions into Chapters. The AdMech won't throw away the concept of (re)developing technology on its own, which means upgrades to Imperial technology.

The Human Webway project is going to get finished, which means fast, safe, reliable travel within its reach.

The Emperor's around to prevent the degradation of Astartes Geneseed, and possibly even create new Primarchs/Legions, or a successor supersoldier project.

No spitting the Imperial Army into the Imperial Guard and Imperial Navy, which means there's better coordination between the two.

Plus, you just know that the Eldar know where to find, assuming they don't have stashed somewhere, a complete STC database for everything.

If the Emperor managed to free the souls of the Eldar from Slaanesh, one major difference? Some of the Eldar would have shown up and healed him, so he wouldn't need to be permanently installed upon the Golden Throne.

He's up and walking, and can put the Imperium back together after the battles of the Heresy. No Cult of the God-Emperor. No Ecclesiarchy. Probably no breakup of the Legions into Chapters. The AdMech won't throw away the concept of (re)developing technology on its own, which means upgrades to Imperial technology.

The Human Webway project is going to get finished, which means fast, safe, reliable travel within its reach.

The Emperor's around to prevent the degradation of Astartes Geneseed, and possibly even create new Primarchs/Legions, or a successor supersoldier project.

No spitting the Imperial Army into the Imperial Guard and Imperial Navy, which means there's better coordination between the two.

Seems reasonable, although potentially too much change for a game. You would probably have to seriously up-power goals - eliminate all Orks, invade the next galaxy (maybe that is what Tyranids are fleeing)

A couple raise dead counters: Eldar or Chaos blew up Horus's flagship with Emperor inside. Eldar feel an obligation to humanity and foresaw the emperor would get in the way. So after he stops Horus they assassinate him, act all outraged, and keep working with humans. They need a crippled superpsychic husk to keep the human web gate from exploding. It's a stasis throne and no one knows how to turn it off. He needs 10k years of peace and quiet so the warp can calm before he Ascends into godhood. Eldar couldn't get to the emperor in time.

Eldrad, Emperor, and Leman Russ went on a 10,000 year pub crawl.

So I plan on running an alternate lore type thing for 40k that I found on 1d4chan, called The Eldar Gambit. The idea is that at the siege of Terra, eldrad makes one final plea to the emperor. No one knows what was said, but when Horus strikes the emperor, the big E uses the sword to travel into the warp briefly and eat slaanesh's stomach, thus freeing the Eldar from She Who Thirsts. As a result, the Imperium and the Eldar are now very closely aligned, with the Eldar being considered a department of the imperium.

Apart from needing some believable lore on how that would change things, what kind of technology would the imperium potentially make since now moving it with Eldar tech is an option?

With this major change, it could be possible that the Imperium's hatred of all xeno's being evil would of been slightly abated, or even made non-existent. Both routes obviously change the flow of the game, as well as technological advances. As you stated though, they are considered a department of the Imperium, so in which case we will go with the later.

Allot of what SpoonR recommended would probably happen. The AdMech might also see the union of Xeno and Human tech as a viable route without calling it heresy, instead of a hidden agenda by some; the Ecc not saying all Xeno's are evil and deserve to be eviscerated; and the Inquisition focusing more on Chaos and warp incursions instead of xeno "taint." Which might include xeno tech from the Tau, and other races open to trade and negotiation, being implemented / combined with Imperial tech and tactics. Heck, if it happened with one Xeno Race, who would think it would not happen with another "friendly" xeno race. So the possibilities are endless here. Psykers might not be as feared as much, as the Eldar could have helped them control their powers. Mind you, this outlook would also effect warp travel, the way ships are created, troops armed, xeno forces working jointly with Imperial forces, etc etc. Off course, I'm sure Eldar influence had nothing to do with this alignment and change of view toward them......

Now, lets take a look at the other view, of where the Imperium's hatred of Xeno's was only slightly changed. It could be that the new Eldar Department is secretive, and very hush hush. With this attitude, what Senshuken and Raidwraith mentioned would be more plausible. Maybe some trade of minor tech or decorate art could of been established. Maybe it didn't hold out, and the AdMech, Ecc, and Inq saw the trouble that it caused and cut it short and reduced it significantly. So, not much has changed, other than a few big wigs getting the advantages, and the local populace not seeing anything major. No combined forces, no merging of Xeno tech, the main hatred of Xeno's still stand, and Psykers are still shunned and hunted down.

So really, you have to look at the view and the stance that the Imperium and the Eldar factions want with each other, before proceeding further on the whole technology combined issue. Happy gaming.

I imagine there would be Eldar who are like "yeah, um go emperor!" One who would say "well I'm going with the guy who isn't going to r**e my soul and puts ten billion screaming fanatics between me and Slaanesh" and then the ones who paint their faces with Aquilas and scream like overzealous soccer fans. I would think imperials work the same, with perhaps the added flowchart of "Is it the Emperor's Will that we befriend the nasty knife ears?" "Yes." "His Will be done."

The Eldar stick around because of the deal they made with the emperor, and that having 1+ quintillion insane guardsmen and another million space marines between you and the gribblies must be pretty nice. And all you have to do is smile and make the sign of the Aquila now and then.

This turned into some weird rambling as I typed, so you're warned; there might note actually be a cohesive thought to it. Sorry folks.

I don't think filliman ever said the Emperor was alive and well, only that he assisted them in wounding Slaanesh and freeing some (or all) of the Eldar souls stuck in his gullet.

Oh the emperor is deader than Elvis. He just saved the Eldar eaten by Slaanesh and prevented more from being eaten.

I dunno why people would assume that anyone would allow a XENOS FILTH to touch the emperor, much less resurrect him`? If the emperor wanted to be resurrected he would have done it himself or let someone WORTHY OF THE HUMAN RACE do it. Or something along that line, I don't think they would ever even let a xenos step on Terra.

Okay.

So its pretty clear this idea is not at all popular.

Not many (me included) are for an Eldar/Imperium grand alliance And GW rather ships blood angels and newcrons. (Argh!)

However! If you really want the Eldar to stick it to Slaanesh, you might actualy get your wish (from GW even!):

In codex Harlequins, there is a line about The Laughing God's final joke: To get Slaanesh (to expend all it's energy) to save the Eldar, rather than consuming them! No clue as to how they are gonna pull that off.

Crazy sh*t like that is why i love them harlequins! None of the other eldar truly believe they can win the war against chaos, except these killer clowns from outer space.

I like it, and with all good things, the unintended consequences are what makes it exciting.

(think simon pegg as scotty, dripping wet on the bridge)

I'm actually a bit of a fan; my brain just wasn't wrapping around how the arrogant, capricious Eldar would be trusted to stay helpful after all 10,000 years, even with those souls being saved, or how the Emperor achieved it. I would LOVE the Eldar to quit being colossal d-bags, and put their dwindling power behind another race, whether it was giving their knowledge and awesome to the Imperium, or elevating the Tau to a more level spot on the playing field, in the places where their better weapons and well-trained soldier advantages help a bit less. Instead, they refuse to, on the grounds that once kings, never commoners, and if it was something that could happen bad to them, why shouldn't others have to experience it. The Imperium MIGHT be forging a new God of Chaos, same as the Eldar did, depending on what you read, and the Eldar are so embittered about everything, they won't tell the universe "yeah, we did that with Slaanesh. You? You might want to rethink the road you are on...it ended poorly for us."

Hell, I'm one of those hammy doofs who has "written" an Eldar/Human romance story, so I'd love the two races to get along. What I read above just confused my likely sleep-deprived brain. Apologies. Of course, GW can be counted on to write every faction as purely antagonistic, just to ensure any army can fight another army, on the table top, and it won't seem TOO out of place. They each get along with a few others a few days of the year, but then they all remember there is not loght in the void; there is only war.

Also the Bieltan would go rogue after five minutes. They don't like them monkeigh.

Funnily enough, I'm in the middle of a pretty big project that's basically an RPG focused around the Eldar. It is absolutely compatible with FFG games, so feel free to use it either as-is or as reference once it's finished (a week or two tops, if it's not done by then keep poking me until i finish it, if you're interested that is ).

As for what changes those events would create, well, I'd say that most of humanity wouldn't see much of a diffrence other than "all xenos suck, except Eldar, Eldar are cool (at least some of them, that is)". There would be a split among the Craftworld Eldar- some would cooperate with the imperium, while others (like Biel-Tan) would rather die than ally with a "lesser race". Human Psykers would be safer and would get better stuff, and the general cooperation between imperial worlds would improve due to (probably very restricted, but still) access to Webway. I don't think the Eldar would rejuvenate the Emperor- Adeptus Custodes would absolutely not let a Xeno in.

I wonder how the harlequins would react tough...

I wonder how the harlequins would react tough...

EDIT: Smartphone, huh? Ya tink auto corect is funy do yeh?