While we're talking about Mordekaiser and Rylai's: My dream of Mordekaiser - an Icy Revenant.
What is cooler than a Huge Juggernaut that brings frozen death to his foes? He just doesn't crush their body, he devastate their mind and souls.
Much like Imlerith or even Eredin (both from The Witcher 3), someone who represents crushing death and abduction, cold and fear, who controls enormous strength and magic. Even the Arthas Lich King (Warcraft) makes good representation of this acrhetype. Anyone who've seen him in Heroes of the Storm will know perfectly what I mean.
Nothing is more Metal (the music) than death by ice. There is even the fact that a lot of metal subgenres and thematics come from the nordic countries.
Here is what I wrote on one of Malicious Metal's thread:
"IMO Mordekaiser could be something like the Wild Hunt revenants from The Witcher. Does anybody know Imlerith? Big metal warrior with huge mace that is slow but deals devastating damage? They also control ice (even freeze things sometimes), wich could give Mordekaiser** CC in form of slow or stuns**. I look at Mordekaiser and also see the Lich King from Warcraft.
That is what I dream Mordekaiser should be. A Giant Metal Revenant from the Cold Northern Mountains/Forests (wich is really metal music by itself) that brings cold death to his foes, crushing their body and soul. This is fear incarnate. Nothing is scarier than frozen death. He could also get some form of fear mechanic in his kit, as CC.
They don't have to force him out of the Shadow Isles for this to work (lore-wise). Maybe he started in the North but ended up there for some reason. This green-greyish thematic from the shadows isles is actually something I'm a little tired of on every Shadow Isles champion. It makes them look TOO similar to each other.
Icey death in the form of Metal. This is what Mordekaiser needs."