We can already guess which champion you're picking.
I do play League of Legends, but I personally don't think the world of Runeterra is a desirable role-playing landscape, and I disagree with role-playing canon characters with firm established personalities written by professional writers, especially when certain events will inevitably happen in the role-play by result of pre-set character lore.
However, this is League of Legends we're talking about, and while there is so much lore in place to establish characters and such, the lore gives us events, not details, leaving it open to plenty of interesting tangents, and it wouldn't take an advanced RPer to improve on the personality of most League of Legends characters.
Which is why I reckon putting it at Casual. Not an easy concept to use, but certainly not a hard concept to get some entertainment out of.