In Yasuo's lore, it states that the old guy who he had to guard was killed by someone with a wind technique. Many people speculated that it was Riven, with a few people pointing fingers at Janna. Does anyone know who killed the poor, dead, senior? Has Riot confirmed the killer?
An extract from 
color text: "[...] The scale and precision of the new device made his previous work with blades seem insignificant by comparison."
And we know that jhin is able to imbue his weapons with wind-like magic so the most believable culprit is him though yasuo doens't know about him (only Shen and Zed seem to).
Dude its riven. If you play yasuo against riven and the riven ults Yasuo will say something about how her technique is familiar.
Who killed elder dragon? Not my jungler, that's for fucking sure.
Or it could be a pupil from the previous generation since it's said that Yasuo was the only student to master the wind technique in a generation.
We'll have to wait a long time to find out.
So, we know 
all utilize wind techniques. There's also the possibility is another potential culprit.
However, there is one other character who has been known to utilize wind in their abilities.
Back before her rework, Karma trained under Janna to master the ways of the wind. It's also why fans were her weapons of choice.
Granted, I don't know enough about the whole Elder lore to have any sort of real theory on how or why Karma might even be a potential suspect, though.
I hunger for more lore on this subject. This has been the only part that I've been truly interested in for a while.
Personally, I don't think Riven did it. If she did, if it were pre-exile, she would have lead a Noxian warparty and completely wreaked the place and killed everyone around the elder, not just him.
Post exile, she lacks a clear motive. What caused her to leave Noxus was the senseless and meaningless killing of Ionians. Her pure Noxian ideal is strength through honorable combat. Slaughtering a single elder achieves nothing for her.
It's not riven. How would riven be in two places at once? She was on the battlefield when that happened and almost got killed. How could she have time to briefly kill the elder than get back to the field? Janna is most certainly not the killer. No in game interactions are entirely canon. Only some because some champions actually have met each other in the lore. The person who killed him resides and hails from Ionia. I'd bet it's a disowned pupil who also knows the wind technique, but was banished because of some reason. The cabal in the Ionian Council could also be behind this given they have down a lot of shady business to begin with.
Currently we don't know and I am pretty sure that we won't know until the end of yasuos story(or at least far later).
I speculate that it's Riven's mentor who could be an Ionian traitor. But that's just pure speculation.
