Who do you think Sylus really is?

I have seen seeing a lot of speculation in this subreddit, but also people seem to be sure about Sylus’ identity. I personally feel like we have yet to encounter him in any physical form.

Also, maybe I'm missing something, but I still don't understand why people are connecting the kidnapper from Chapter 8 to Caleb to Sylus or the kidnapper to Nero to Sylus. Like, how can anyone be sure that the kidnapper mf is Sylus?

Like, I get that Nero is suspicious asf and that the kidnapper kinda sorta looks like Caleb but.... is it just speculation that the kidnapper really is Sylus?

Also, how are the Sylus stans holding out?