Any explanations? I saw thresh has the key around his waist and fiddle has a similar looking key on his neck.

It's the key to the bathroom at the institute of war. They give it to Fiddlesticks and Thresh to make sure no one steals it.

Keys are like the bling of scary champions. I don't think they actually unlock anything

bump for awesomeness

Thresh's key opens the lock to his lantern. Which... doesn't seem to be locking anything.

Thresh's is a Warden's Skeleton Key and Fiddles is to unlock his master's chamber. (In the lore, Fiddle's master is a deranged summoner who broke everything to bring in Fiddle. The only way said summoner stays in the League is because he is locked in his chamber.)

well i know thresh has the key to my heart <3

keys.
keys start with K.
Kogmaw starts with K.
kogmaw is from the void.
Chogath is from the void.
chogath can mid, top, and jungle.
going from mid to top: rising
rise:=> sounds like Ryze
Now, cue the dramatic music.
Ryze leads to:

From Ryze, we begin the theory. watch the video to learn

It was Singed the whole time. He planted the keys.