I have TI4, but I wasn't exposed to the game before this edition, thus I think it's fair for me to say that there's no reasonable route that I can find to get and read the lore that was published with the out-of print games, such as TI3 and it's expansions.

Are these files uploaded somewhere in the public domain? If they are not, then @ FFG - Could you consider uploading them?

Obviously, I understand reservations on sharing games that FFG might reprint, but I don't think that all of them fall into that category. Maybe a lore compilation is something that FFG could sell?

There was a lore compendium included with TI4, but that does not include the narratives from Shattered Empire, Shards of the Throne or Rex. These can be found if you just google them. The short story from Rex is the best written, IMHO.

Are @FFG going to give us another dose of lore with upcoming expansion?

As seven new races with presumably new abilities will be introduced, the answer is yes. There's already been speculation about the characters depicted on the leaked box cover (including Space Paladin, Cat Person , Thorny Beast, etc.). We'll see what Dane has gifted us with when the expansion is released later this year. 🖖

If there was a wiki for Twilight Imperium that includes 2nd and 3rd edition components I am sure you can find the lore there.

But yeah there isn't a tome as much as there is a codex, so finding lore for Twilight Imperium is like cyphering the dead sea scrolls.

The biggest chunk of lore is probably the racial backgrounds on the race sheets in the game, and those are the same in both TI3 & 4.

There was a second game set in the universe called Rex. It was a reskin of the old Dune game. Presumably it had some more lore, but I never got it to see how much was new.

There is a TI novel coming out soon that I imagine will expand the galaxy a fair bit. Fractured Void.

https://www.amazon.com/Fractured-Void-Twilight-Imperium-Novel/dp/1839080469/ref=sr_1_9?crid=1C8KU15WEM9TE&dchild=1&keywords=twilight+imperium&qid=1600778170&sprefix=Twilight+imp%2Caps%2C204&sr=8-9

Much, but by no means all, of the old lore from TI1 and 2 can be found digging around in the files and images associated with each individual game on BoardGameGeek. You should be able to find the rulebooks in the "files" for each game -- the stories in the rulebooks for TI4's "Distant Suns" and "Outer Rim" expansions are worth hunting down -- and the faction lore for TI1 in the "Images", although the faction lore is pretty much a stripped down version of what would later develop for TI3/4.

You can still (at the moment) find copies of the TI3 rulebooks from FFG. The base game lore in the rulebook and on the faction sheets is NOT identical to that in TI4, but is very, very close. Unless you're working on a project examining detailed changes in lore, it's not really worth examining. There is a lot of tiny lore blurbs on the political and action cards in TI3, but short of buying the game and all expansions, I'm not aware of any way to access those (legally or illegally, for that matter, not that I condone pirating TI). The TI3 Expansion rulebooks with their accompanying short stories others can be found from FFG here:

https://www.fantasyflightgames.com/ffg_content/Twilight Imperium 3/TI3_SE_Rules.pdf
https://images-cdn.fantasyflightgames.com/filer_public/3e/e0/3ee0957b-a4bb-4615-8519-c1540d152225/shards-of-the-throne-rules-low-res.pdf

TIRex was 100% new lore, with short faction lore for all six in-game factions and a pretty dark extended short story at the end of the rulebook about the overthrow and genocide of the Lazax, presented from the point of view of a Lazax magnate on Mecatol Rex. I'm not aware of anywhere to get the faction lore outside purchasing the game, but the rulebook can be found from FFG here:
https://images-cdn.fantasyflightgames.com/filer_public/bf/22/bf22a60c-004e-4f12-a224-1ba003461114/rex_ruleboook_web.pdf

There were also some other spin-off games -- the original RPG has been explicitly and enthusiastically de-canonized (I've never encountered a copy), and is -- based on what I've heard -- not worth reading for casual interest, even *if* you can find it. There was also TI: Armada, which -- as far as I can tell -- is mainly interesting only in that it gives the names of a number of ships and characters, with no real narrative detail.

You've perhaps already seen by this point that it's been confirmed that the new expansion will include an additional lore compendium, and there will of course be the lore on the backs of the new faction sheets; the Naaz-Rokha stuff has already been revealed on Dane Beltrami's twitter feed.

Thanks all for the replies!!

In case anyone comes back to this thread, hopefully they see the Guide to the Imperium file that was added to the TI4 product page.

https://images-cdn.fantasyflightgames.com/filer_public/b6/d9/b6d969a2-21c2-4b1e-8d6f-ac6fec456b88/guide_to_the_imperium_10_web.pdf

^Uploaded on October 23, 2020 - Thanks, FFG!

Also, they have released a novel set in the Twilight Imperium universe called The Fractured Void, that can also get some fiction into the universe.