What if Fiddlesticks voice was more like the predator mimic voice's.

Where he can't even speak for himself like a crow but use's miss matched lines from people he killed in the past like how a crow can learn to mimic human words.

Even disregarding context like when he ults he screams "What is that thing" in the voice of a scared man that's slightly distorted. or other quotes all with small story's attached to each of them, maybe he has a quote where he says "come on you think that crow monster is real?" said in a calm female tone or have him randomly scream for help in a child's voice.

I think stuff like that fit great with the second part of him meaning to be a ambusher where he slowly picks people off one by one using there voice to trick there friends who are still alive into thinking they need help when they are already dead. using the screams people made as they died to put fear into the ones he hasn't gotten to yet.

you can even have a gimmick in game where his taunt has a distorted voice line of the last champion he killed so like say he has a normal taunt that doesn't really need him to say anything, but if he kills a Garen then while he is doing his normal taunt he also says "Hey, look, I'm holding the world up." in a distorted tone.

predator clip for more of a example https://www.youtube.com/watch?v=O8Is7peYWAM

P.s remember tax bird he is true terror