Veigar 
is actually a good guy when you think about it.
He wants to unite all of Valoran under one peaceful rule, he just believes the best way to do it is to use force, since that is all anyone understands. That explains why he is insulted when someone demeans him, he wants people to follow him, he just believes that fear is the best way...
We all know Teemo is the real evil here.
Sivir is the grand grand grand daughter of Azir's brother who was the a captain of the guard and the High priestess who was a barrier maiden. They survived the fall of Shurima thanks to the High Priestess' Spell shield skill.
Sivir was taught the high priestess' spell shield but it's much weaker because she ran away to become a mercenary. Sivir took to her great grandfather's side and wields her inherited boomerang blade as a heirloom.
Also Amumu
probably was a kid of a horrible pharaoh. One that made a wizard mad enough to curse his son to wander alone forever without any friends...
Lately I've been very interested in 
, not because I play him, but because I play 
. It had randomly occurred to me that at one point in time, one of them approached the other an was like "You know what we should do? We should make a heavy metal band!" (since, according to old lore, Mordekaiser and Sona were the founding members...so does that mean Morde was the original lead singer, or did they just do instrumentals?)
Regardless of who approached who first, this ultimately must mean that Sona has balls of freaking steel. Like, Mordekaiser's lore is basically Riot saying "Yeah, we don't know who or what he is, like he might be human or he might be some undead demon general thing, idk, BUT WHAT WE DO KNOW IS THAT HE WILL KILL YOU FOR THE LULZ AND EVERYONE AVOIDS HIM LIKE BRONZE 5", so for him to come up to Sona (or Sona to come up to him) and be like "Let's make music together! :D" and Sona didn't immediately crap her dres and flash away in the other direction, like...seriously. Sona has balls of steel.
So naturally, that one funny thought led me to try and figure out what Mordekaiser actually is. I might have mentioned how useless his lore is for determining that, and the most anyone can maybe get from it is that he might be bound inside his armor via a curse--which would almost seem viable since all of his skins show him in armor...except for the Pentakill skin, where he is shirtless (no wonder everyone thinks he is not human. because them abs are outta this world ba dum psh), so clearly he has skin under there and it looks, for the most part, human (I dunno what's going on with that Michelangelo abs on abs stuff...rito plz learn how anatomy works).
I dunno. I'm still trying to figure Mordekaiser out. He is like a very complicated puzzle with several missing pieces...
Summoners are actually the Protectorate and Magelords indicated in Aatroxes lore and one of their battle grounds is the Summoners Rift.
In 
's updated lore, I have a theory that the young Yordle who re-purposed Heim's ball pitcher into a makeshift turret is actually 
. And that when Rumble was younger, he actually looked up to Heimerdinger as a mentor, and felt betrayed when Heim left Bandle City.
Not the most interesting headcanon I know, but eh, you said anyone could join. =\
My personal head cannon is that Kalista knew hecarim in the live olden Shadow Isles. I believe he was one of the few responsible for her death.
Boram Darkwill was a menace who had to be removed, and Swain was the only one actually capable of doing so. Swain's original motive behind aiming for Noxian High Command was to get vengeance for Riven after he found out that NHC were responsible for her supposed death (mainly out of respect and admiration for her, I mean she was the poster girl of Noxus and NHC completely removed her). Just my own thoughts.
Kog'Maw is pretty much Stitch. https://www.youtube.com/watch?v=oaa_jzILsuo
Teemo brought Rune Magic into this world, and he seeks to destroy the League so it will be used once again.
Jax is a purple melee minion that somehow broke free of Nexus magic and survived numerous League matches to become a champion in his own right.
Veigar is a blue caster minion who went mad from the numerous league matches and somehow was deluded to think that he is a yordle
OR
all the blue caster minions are in fact yordles that became enslaved by Nexus magic and Veigar is simply the only one that stands out
Lollipoppy is a marketing ploy designed by Demacian propaganda masters to gain sympathy for the Bandle city cause.
It backfired spectacularly.
Nowadays, Poppy only wears her Lollipoppy outfit when she wants to terrify Noxian soldiers.
was eventually took in by the Yordles where he is being studied by
However, since is the only recorded being who ever broke a shard of true ice, he will probably be instrumental in the fight against Lissandra and the watchers.
Omega squad teemo follows the battlecast/fullmetal skin timeline When Biktor first comes to power Teemo offers himself as a sacrifice to keep Viktor from attacking bandle city. However he is turned into a cyborg killing machine for any who appose the glorious evolution. Champions from all of valoran try to reason with him after the transformation including ALMOST every girdle champ. If you look in the spoils of war bundle you can see a champion from every region. Amumu was sent from shurima since azir thought yordles could talk better to each other even though Amumu might be human, but he looks like a yordle. Gragas was sent from the freljord to try and get Teemo drunk to be reasoned with better. Akali and Caitlyn were both seen as good enforcers of law so they were sent. Gangplank ( probably now king of the Pirates) went to represent Bilgewater. Dr. Mundo even went with a back up potion to kill Teemo if things went wron ( not knowing it won't work on a cyborg). Alistar and Annie went ,as they were the only champions from there regions. Malagueta went simply to preserve peace. The void-born even sent Kog' Maw (him being the void equivalent of a cute puppy) because metal cyborgs are no fun to eat. However they later find they can be improved by metal thus joined Viktor as battlecast versions of themselves.
Now I believe that we may find an omega squad Ziggs and Rumble since they are the only yordles not in the spoils of war bundle. Maybe even an omega squad Veigar and Lulu even though they aren't usually affiliated with other yordles.
Then Teemo shot him down..
and are long lost orphan sisters, both growing up in such differing environments, their personalities changed from each-other very drastically. After meeting for the first time and learning of her parents hiding her sister from her, finally went off the deep end into a pit of anger and depression. This being hidden by a mask of childish humor to the situations she faces, Jinx forgets her real name, and wreaks havoc in the hope that her parents will show up to stop her, and take her in like she always wanted.
