Possible Shapeshifter Champion? (Champion Concept)

So I was watching this video by Jeremy "Gaming Curios" about how Riot had originally had a plan of a shapeshifting champion that was different than Gnar. While I was watching he spoke about a possibility for a champion that had the ability to transform into a demon form or something like it. He mentioned however that the champion Riot seemed to be looking at was a more tanky support like champion. This reminded me of an idea I had gotten a while ago that I thought would be an interesting addition to the League roster.

As of now as far as I understand there is not really a champion who plays off of the characteristics of being a really good person who wants to help people and do what is right but struggles with an internal darkness or demon that plagues them and causes them to do things they don't want to do. I thought an interesting champion concept would be a knight like character or paladin like person who was born with a prophecy that he/she would bring either great light or great darkness to the world of Runeterra. In this, the character would be under this curse of a great dark power dwelling inside of them that can sporadically take over their body and cause them to do things completely different than they want to do. This person themselves wants to do good and protect the innocent but this darkness inside of them wants the opposite, to destroy and terrorize. This kind of dynamic is something I don't see in any other character in League of Legends and something that I think would be fun and something many could relate to as well in those moments we want to do good but evil crouches near us at all times.

I thought this character could be a tanky melee character who could be played top or support but who with their ult, could temporarily transform into a completely different playstyle, something more akin to an assassin or simple burst champion. Now I haven't thought of all the logistics but I think that this transformation could sacrifice his tankiness temporarily to make the character faster, more damaging and basically more scary. When he transforms there should be this feeling of, "Oh no, he changed! I've got to get out of here!" playing off of the players panic. Thus players could still react after the character changed but would have to choose whether to fight him now that he has transformed at their own risk or get the heck out of there. Other than that transformation ult, I'm not sure what else he could do with abilities, you could play off of the good/evil dynamic even more and make the good side use light as a weapon and the bad side use darkness. Thus un-transformed he could use things like slows, blinds or stuns to get in on his opponent and fight close quarters, protecting allies and peeling for his frineds who he wants to protect. Than when consumed by the darkness he could be a gap closing monster that leaps around the fight and his hard to lock down for the brief window of transformation.

This is my first time posting and idea so I have no idea what comes out of it but I think this kind fo champion would bring a new dynamic to League of Legends and utilize some of the ideas Riot has already had in the past.

What are your thoughts, because I'd be glad to hear them. :)