Several Ideas, feel free to comment.
I've been working on these ideas for a while, and I wanted to see what the League Community might think (and maybe see if Riot would like them)
I have 3 complete champion ideas, and one that is incomplete, as well as a gamemode idea.
I'll list an overview on each one on here, but link the google docs that have information on their abilities (please not that the numbers for damage and stuff are just placeholders). Please feel free to leave comments or suggestions!
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Idea 1). Cier, The Trueflame Guardian [Support/Mage]
Cier was the first and favorite of my ideas, the ideas for his kit have varied, but I think I like where it turned out. I also though it would be interestig to have a nemesis for 
. As well as maybe provide someone who helped with his capture and binding to the League.
I also wrote a lore for him: In ancient times, there was a group of remarkable mages who stumbled upon a different form of fire. This unique fire, which they named the trueflame, was crimson in color and highly volatile. Pledging to use this newfound power to protect others, the mages formed the order of the trueflame and they traveled through the land helping others and offering teaching to those who showed promise. One especially talented young boy, Cier, was especially apt with the trueflame. To fully learn of this power Cier left his family and his village to travel with the mages and learn about this amazing power. They taught him everything they knew. One day when Cier was out exploring in the nearby woods, a group of hostiles attacked Cier’s mentors. A fight ensued, killing everyone except one enemy: Brand. When Ceir came back from his exploration, he saw a glimpse of Brand before he got away. Before Cier could chase after him, one of the mages called to him for help. Cier tried to heal him, but the mage died from his wounds. Before the mage died he told Cier what had happened while he was gone. Angry, Cier pursued Brand all across Valoran. Eventually, Cier joined in the Rune Wars on the opposing side of Brand. When the two met in battle, Cier managed to defeat his foe, only to have Brand laugh and say that he would be back. Worried that Brand would actually come back someday, Cier used a talisman to store and harness the energy he would use to stop his aging. The endeavor succeeded, and when Brand indeed came back, he assisted the Demacian forces in capturing Brand and confining him to the League. Worried that this wasn’t enough, Cier joined the League himself, determined to keep a close eye on his eternal enemy.
I'm no artist, so I don't have any concept art, (sorry, but my strengths are in storytelling and coming up with ideas) but I imagine Cier as a younger man with bright red hair, wearing white robes with red trim and a red staff made of wood.
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Idea 2). Melore, The Dagger Assassin [Marksman]
Melore is an assassin known for his aim with a dagger. He his affiliation with Noxus means that many of his targets are Demacians. Melore prefers to stay in the dark as much as possible, few know of him, and fewer know his name. Not a man to stand up in a normal brawl, Melore prefers to kill from a distance, usually without anyone ever knowing he was there, even after the killing.
Melore's parents were killed by the Noxian High command for speaking out against some of the brutal campaigns they were waging against other factions in Valoran. Instead of seeking revenge, Melore figures it's better to work for them (for some odd reason)
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Idea 3). Arerow, The Roving Blade [Fighter/Tank]
Arerow is interesting for me, he's the idea out of the main three that I've spent the least on Lore-wise, but the one that I've spent the most on ability-wise. His kit is really about being able to sustain a lot of damage and having a decent gap closer, making him a possible good pick against high damage top laners, maybe even some of the ranged ones. His kit might also work nicely in the jungle, because of his sustain from Self Defence. Another great thing you could focus on about Arerow is the variety of ways you could build him. Going full tank allows Stance and Self Defence to protect against high amounts of damage, while building as a Juggernaut, with more AD allows Stance's Lunge mechanic and Blade Thrust to deal more damage, while keeping some of the protective stats of the other abilities in the kit. Using Arerow's ult Roamer's Instinct can play to both of these playstyles, and ulting at the right time is critical.
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Idea 4). The Champion Without a Name Because I couldn't think of One [Mage]
This idea is actually something I think would be well suited to the Ryze Gameplay and Visual Update if you wanted to revamp his whole kit. Otherwise, I guess it could be thrown in an idea bin. I think the passive on this idea could lead to some interesting builds.
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Idea 5). Nexus Siege
Nexus Siege is a gamemode where one team is basically trying to beat the clock and the other is trying to wait it out.
It's alot more interesting (at least in my opinion) than the TL;DR above. Here is the Google Doc
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If you read all this thanks for your time, and feel free to tell me what you think.
~Fire
P.S. Here's a little thing for Riot, if they need it: Here you go