I can only provide the ideas, I'm bad with the stats and so forth, so if this ever catches wind I leave it to you lads.
Okay, lets get started.
I'll firstly describe what he is, I intend for this champion to be a number of things, but at heart a melee fighter, with the option of AD, AP or a mix in the roles, used to 'melt' the opponent and chase down, using the power of his corrupted fire and his trusty, ignitable blade.
(Make note, I haven't given the abilities names, because I'm not sure what's appropriate, well except the ult)
Passive: Fire created from abilities inflicted onto opponents can be spread to Ignis via Auto Attack, thus igniting his blade for 5 seconds, striking the same enemy will keep igniting the sword, but the opponent can only be ignited once, until struck again by an ability, auto-attacking a none-ignited foe will cause it to be set ablaze one for a set time, until struck with an ability. (lets say after 10 or so seconds can another AA-ignite be inflicted)
Ignition damage: A set amount plus a small percentage of your base Ability Power.
Q: Ignis shoots a fireball from his corrupted hand in a skillshot, dealing a set amount of Magic damage and igniting the struck foe. Alternatively you can cast it on yourself to ignite your blade.
W: Ignis slashes in a cone dealing AD damage, if your blade is ignited the length is increased, dealing extra AP damage as well as setting ablaze foes whom are too chilly.
E: Ignis dodges in a line, leaving behind a small trail of fire, which burns out....pun......after a few seconds, slowing and igniting any enemy who walks through it.
R: (Wildfire) Ignis warps to an enemy, then releasing a huge explosion of fire in a radius of the targeted champion dealing tons of burnies (AP damage) in the radius and igniting them all. IF!!! Both Ignis's blade and the opponent are both on fire, the target is stunned for 1.5 seconds (this may be taking it too far)
Lore, this will also explain what he looks like...I'm not a great writer, but I'll try.
"Next we all knew, Kegan exploded into flames after touching that cursed flame, killed half of us....we don't know what became of him, a demon?"
Ignis a crewmate of the Marauder Kegan Rodhe was one of the few who survived his former employers choices, seeing the flaming phantom burn a path into the distance, those who survived went their own ways, but Ignis left burnt by the blasts and unconscious awoke an unknown time later, with a glow in his right arm, yet burnt and unable to use it, he wanted answers for what he witnessed, and followed the clues, the baron burnt scars and the dead. On his journey Ignis felt rage grow in his, and heard a voice, a burning vengeance "Overcome the flames, destroy the Brand"
His arm grew into an abomination, a twisted burning pain, left him outcast to the common folk, reaching a land called Valoran he found the answer he seeked, the arrest of a flaming spirit, cursed to fight for The League.
On his journey to find this league he encountered a budding scientist called Viktor, seeking the same prize, amazed by Viktors lack of disgust for the deformity Ignis bare, but saw it as a fault to be perfected, and forged him a hextech blade, powered by the immense energy that the corruption produced, the blade helped Ignis to channel his power that he was bestowed on and thus aided him to focus the destruction, whereas...Kegan could not.
The two ventured forth, each to their own goal, Ignis, satisfaction for the rage caused by the corruption that was spread to him, and perhaps answers on how to extinguish the flames within him.
_"The flame can spread, to bad Kegan, you created the Wildfire that will smother you"_
From that I will try and make a depiction of Ignis, but you can all make your own interpretations, but I am eager to give an update soon, and as always your views are valued and appreciated.