Conspiracy theory: The Crownguards killed Jarvan III
Specifically Tianna Crownguard/her husband. We know now from Aftermath that Mr. Tianna Crownguard was the head of the mageseekers. We also now know that Jarvan III was going to have the mageseekers halt the arrests of mages.
We can’t say for sure that they (the crownguards) knew about that last bit, as only Xin Zhao and Jarvan IV are seen to have read the letter. What I can surmise is that someone had an idea of what Jarvan III was going to do.
Now we have also seen in Aftermath that both Tianna and Mr. Tianna (I don’t remember if they revealed his name) are advising Jarvan III on how to deal with the mage rebellion, and that can’t be good.
Edit: I’m also adding that Tianna at least seems to hold ambitions for the throne, hence recommending that Lux marry Jarvan III
: a mage and unintentionally the instigator of the rebellion that, supposedly, led to the murder of jarvans father, lux will have a very hard time convincing jarven or any highly influential member of Jarvans court to sow for peace.
: guilty over not be there to prevent jarvans fathers death and although many do not blame him for the death of Jarvan the third , some (particularly aunty shoulder pads and her husband) will and likely remind him of the fact should he openly speak out against whatever harsh move that jarven makes on mages as well make any suspicions he likely has about the kings death seem weak
: Despite all the possible references to shyvana in the comic, I doubt she’ll be there at the last minute to help fight the uprising and may only come in the aftermath. Should she do so her being a magical creature will not help matters as jarven has now taken a dim view of magic and that fact she was not there will make others believe she left demacia (and jarven by extension) when she was needed most which will make whatever concerns that she may voice seem hollow and self serving as she is speaking on behalf of her fellow magical beings and not on the interests of ‘true’ demacians
: I believe that there is a higher chance of jarven convincing garen on taking about peace with mages then the other way around but since garen has such a close friend of jarven and since I don’t know what the next step in the story will be, garen changing his views will have a very big impact on jarven cause if someone like garen who has made no secret about his view on mage could be made to sympathize with mages then why can’t jarven be made to do so again.But as I’ve said before it will take something truly momental to change gardens views especially after whats happened recently
: we do not yet know if Morgana will try to directly try calm the situation of the civil war of if she will do so from the shadows but despite her genuine good intentions for demacia, legends have portrayed her as the dark evil sister in demacian stories which will make it hard for some to trust her or her intentions
All in all things seem grim for demacias future as forces both outside and within will seek to tear it apart
Leblanc killed Jarvan.