Swain has just recently hit the Public Beta Environment and his interactions are a treasure trove of lore secrets. Thanks to his W ability, Visions of the Empire, Swain is able to peer into the mind of the players he strikes. When he hits Irelia with this ability, he teases a fun story that we’re likely to see from the upcoming Irelia rework.
When W hits, Swain says to Irelia:
Am I to seek revenge for my poor departed arm? If anything girl ... you did me a favor.
This tells us two awesome things about both Irelia and Swain. The first is that Swain is actually missing his left arm. You know, the one that glows and is scary looking. It seems that Irelia relieved Swain of his arm, most likely during the attempted Noxian invasion of Ionia that we’ve heard so much about over the years.
The second thing we learn is about Swain’s new arm, the creepy one. It seems likely here that, based on some of the other lines from his interactions, that Swain has replaced his left arm with some form of demon.
So, without Swain’s lore even being out yet, we know that he and Irelia have battled and that Swain became a magical being after their encounter took place. Quite the interesting tease of Swain and Irelia’s back story. We should know Swain’s full lore soon, with Irelia’s coming later this year.