So, seeing as how I've been running through my lores, I came across Caitlyn's "nemesis" of the mysterious C. Any champion going to come out of that or is the identity of said person/yordle/whatever remain unknown? I don't think I see any champions whose name begins with C that could be the potential culprit.

Caitlyn.

Who better to chase after and improve your detective skills than trying to follow yourself? Or what is the point in being the hero if you don't have a villain?

One of those *What if* things, but we'll never know for certain. (Not my personal opinion though, just something someone once said)

C is probably just one of those open ends that Riot likes to leave open in case they run out of inspiration for a new champion. There are plenty of potential lore-based champions like that. Aka The third Frejlord Princess/ Ayelia/ Irelia's Bro/ Kass' Daughter, stuff like that.

kass' daughter is dead, if you read the journal of justice she was killed by malz

she was just sent to the Void by Kassadin himself

At this point, it might possibly be Vi.
http://www.youtube.com/watch?v=1ZtjcExwNRw

A card with the letter c from Cardmaster. The nemesis is Twisted Fate he is the only one even related to cards in the whole game.