Trust me, you should rewatch the Elden Ring: Shadow of the Erdtree cinematic trailer after beating the expansion

Elden Ring: Shadow of the Erdtree's cinematic trailer dropped exactly a month before the expansion's release, and the collective response was about what you would expect: "This is rad, but I have no idea what's going on." Now, though? Well I have kind of an idea what's going on after spending 80 hours or so in the DLC, and it's all about as grim and unsettling as you'd expect.

Spoilers for Shadow of the Erdtree ahead.

Right off the jump, we now know that the bloody gate of corpses Marika is hanging out around at the beginning of the trailer is the Divine Gate from Promised Consort Radahn's boss fight at the top of Enir Elim, only when we get there the bodies are calcified and bleached white by the ages⁠—in this primeval moment, the monument is still slick with gore and viscera.

Item descriptions and other tidbits from the DLC reveal that Marika came from a place called the Shaman Village, and that the hornsent society systematically rounded up the Shamans to butcher them and put them in great jars, making Marika's story, whatever her later excesses, one of revenge⁠—think what happens with Paul Atreides in Dune and you're pretty much there. 

My interpretation is that the jars were the prototypes or collected building materials for the Divine Gate, but Marika snuck past or tricked the hornsent to steal godly power from it⁠—possibly that golden thread she pulls out of a yonic flesh thing at the very beginning. One complication is that in-game, a lot of the petrified bodies around Radahn's arena have hornsent horns.

The sequence of Messmer burning down Belurat has always been pretty straightforward, but as NewArtificialHuman points out on the Elden Ring subreddit, there is one moment that takes on a shocking new importance only after playing the DLC. The woman shown cradling a spear at the 1:16 mark is late expansion boss Romina, Saint of the Bud, pre-Scarlet Rot scorpio-centipedification⁠—there's just no mistaking her distinctive Poleblade of the Bud, whose item description includes the line: "Once, in the crumbling burning church, Romina held the bud in speechless silence."

It seems like the burning of her church⁠—which is close to but hundreds of feet above Belurat⁠—was the work of Messmer and his soldiers, potentially even unintentional collateral damage. I'd just assumed it was the hornsent who burned her church, but now it looks like Marika's own forces were responsible for creating, releasing, or at least significantly empowering the Scarlet Rot that would later afflict Malenia and The Lands Between. After that point, we're no longer in lore revelation territory, though we now know that the woman falling through a purple haze is St. Trina. Otherwise, it's just some pretty shots of areas from the DLC and our NPC companions. Boy, I sure hope nothing bad happens to those guys!

I don't know what else I expected: FromSoftware's pre-rendered intros/trailers only ever make full sense in hindsight. Sekiro's intro? You're not gonna really internalize that you're watching Sword Saint Isshin killing an Interior Ministry general until you're like, 40 hours in. The 2021 Game Awards story trailer for Elden Ring? Yeah, that stuff only really fit together after release.

Hell, thanks to an item description from the DLC, we've just gotten one final revelation from that 2021 trailer: Just as Malenia lands on Radahn and stabs him before unleashing the Scarlet Rot bloom, she says something to the general you can't make out in the trailer. According to the description of the Young Lion's Set, it was "Miquella awaits thee, O promised consort." ????