What if Fiddlesticks is the "darkness" that Swain has foreseen?

With the recent revelations we have gotten from the Roadmap came an update concerning our beloved Fiddlesticks, resident devil-out-of-nothing, harvester of mankind, and bringer of death and madness.

There has been a certain amount of speculation on what the threat that Swain has glimpsed through his scrying is supposed to be, the most common answer given being either Mordekaiser or the Void. Others have speculated about it being the Darkin, demons, the Black Mist, the Swimming City, or other, more specific assumptions. According to Interlocutioner, none of these guesses have been right.

So, what if it's Fiddlesticks?

Fiddlesticks is supposedly an ancient evil—a darkness from beyond mortal comprehension, incalculable and inexorable, a portent of extinction to mankind that appears out of nowhere and has unknown motivations—and a danger which is seemingly not connected to any monsters we have learned of so far. Fiddlesticks isn't a demon, a horror of the Void, or a fallen Ascended: he is a wholly different sort of enemy for Runeterra to go up against.

Fiddlesticks' narrative is supposed to draw upon cosmic and religious horror, and his lead writer has expressed a desire to turn him into a proper harbinger of dark times ahead, a being that heralds the coming of greater terrors, which is also thematically cohesive with his gameplay focus of jumpscares and the spreading of fear in enemies.

Fiddlesticks could perhaps be a representation of the formless chaos of existence, the absence of sanity and logic, the concentrated discord of creation, or another darkness entirely, but he may very well be what Swain is so worried about. For, if such a nightmarish apparition is merely a harbinger of worse things to come, what kind of abominations could possibly be lurking on the horizon?