Interesting about the Ruined King as a champion.

Ezreal has his Blade in Legends of Runeterra. It was confirmed that everything in LoR is considered canon, though a lot of things have a "what-if" or future implication that may not accurately represent the current lore. I think Ezreal actually has his Blade, because there's the other (cooler) half to the theory, and how it can affect his design.

The Shopkeepers with LoL have his Blade too. Yeah, the game itself (particularly champion interactions) is not canon; but just like lore influences the interactions, something cool can be done here. At the start of the game, the Ruined King does not wield his own blade, but rather a very... typical-looking spectral sword of some kind. When he purchases it from the shop, he gets a visual update such that he IS wielding it (for skin purposes, his model's sword appears to upgrade at the least). Of course, this implies that he's likely to be a Skirmisher, since they among melee champions more often include it in their builds, and he may passively have extra interactions with it's stats or affects unto his abilities.

"Ah, yes, I've been searching for this since that idiot stole it from me."

"The ultimate blade wielded once against by it's true master."

"What? How did you get your hands on that?!