Did a little research, and by definition, the villains from the Slenderverse, or ARG's, are based off of a much different subject on the internet, so, no, they're not Creepypasta villains (aside from Masky and Hoody, as they are commonly used characters within several Creepypastas)
Idk, whoever it is can turn invisible, either that, or some other reason the people don't react to it. Vinny and HABIt refers to them as "things", and that one time one tried talking, he just gurgled.
I've got no clue, maybe its a thing we don't know about just yet that exists in the Slenderverse.
If I had to guess either, Firebrand, or The Rake, I'd say its most likely Firebrand, considering he can somehow turn into a bunch of eyes, and he has the powers of a Revenant, meaning he could probably pull some freaky shit and make himself appear normal at times.
He seems pretty antagonistic in the new TT entry, "Fortunes", when he's singing at the beginning and how Noah talks about how he possesses him. Hell, by the sound of it, he might have been the one who killed Kat.
He could be the main antagonist in season 2, considering season 1 ended with the reveal that he is Noah. Then again, with how long its been going and how popular its getting, i have no idea how long season 2 will last and if theres going to be another season.
He would be the best "Evil Twin" villain in the Slenderverse...... much better than The Keeper from Pfleming2004, worst Slenderverse ARG ever, even the revelation that The Keeper is the main protagonist was highly based on TribeTwelve, almost identical
I have a theory about Solonor: He comments on everybody's Slenderverse ARG because he wants to do a "minor crossover" with them. I also have seen in a Wiki that he listed Nevil from StrangestPeople12 as a bad guy in his own ARG (what obviously isn't true and he has nothing to do with StrangestPeople12)
lol i guess that Victor is the most recurring character in the Slenderverse, making him one of the major figures in the whole Slenderverse. He can even be the tertiary antagonist of the Slenderverse, after Slendy and HABIT
Cool. The only problem of some Slenderverses are the storylines, seriously. The Angel's Game/APColletion are a great example, the storylines of these series are confusing as hell. People still think that The Creature is Slender Man
but seriously. In my opinion, Humanity's bad HABIT is the greatest villain of the Slenderverse, he's unique and is one of the few characters (if not only) that might be more powerful than Slender Man himself. His vast dark powers even rivals to Slendy's, he can possible be the secondary antagonist of the whole Slenderverse.
At this point, Its safe to consider him that. He's been in 3 different ARG's, and like you said, he may be just as powerful (possibly even more powerful) than the Slender Man. HABIT is definitely the most well developed villain in the Slenderverse, and I'm happy to see his page is becoming more popular on here.