So the thing I look forward too the most with reworks/new releases in the special interactions between champions, and given Swain's position, I've been itching to see these. Thanks to SkinSpotlights for the quick release, and without any further ado, let's interpret Swain's special interactions:
Here's the video in case you want to watch.
The most immediate one that stood out to me is the very first one with Kassadin: "So he heard the rumors, the girl who came back." As we know, Kassadin has a daughter who was lost to the Void, and when Swain refers to a "girl who came back" it logically follows from the context that he's referring to a girl who came back from the Void. This can be interpreted as being that Kassadin's daughter is alive, or that a completely separate girl has been tainted by the void and returned. Either way, this hints at a future female Void-corrupted champion potentially, so that's pretty dope.
Another interesting one is with Fiora and her spurned suitors. I don't entirely know what Swain's hinting at here, but I interpreted it as something to do with her sexuality.
Gonna keep watching, will update as I go along. These lore bombs have me moist.
EDIT 1: So this is interesting, with Jinx, he refers to "faces, fading into flames" and says "it was all her fault." All we know about Jinx is that she has a connection with Vi and that no one really knows where she came from. This could mean that Vi is the person who is at fault for Jinx's descent into madness, or at least played a role in it.
Additionally, there's one with Katarina where he states: "He asked her to do what he could not, to kill me." I interpret this as Katarina's father, General Du Coteau tasking her with killing Swain. Urgot says in his interaction with her "I hope your father begged when Swain betrayed him" so there's a possible connection there. This is spicy stuff bois.
Edit 2: I forgot one, with Darius "No daughters. Only soldiers." Gonna be honest, got nothing with this one, maybe something to do with that comic?
Edit 3: Irelia cut off his arm apparently.
Edit 4: So Kat's dad is dead, and Swain is accused of killing him, says he didn't do it though.
Edit 5: So Swain considers the Black Rose/LeBlanc an enemy/thorn in his side.
Edit 6: He refers to Singed as "Darkwill's loose end," and states that he's not supposed to be alive. Darkwill was the previous Grand General if I remember correctly, hinting at collusion between Noxus and Zaun, and making Singed quite old. Also apparently Swain killed a bunch of Vastaya.