When I first wrote my story, the main villain was introduced very early. Now because I split off the 1st act as it's own book now the Villian is in like two scenes the very beginning and end of the 1st book. He is more in the background that led to the circumstances for the main character but isn't directly involved in the main plot whats going on. If I leave the main villain in there he will be a big question mark for the reader "Who the hell is this guy?" as for the sequel. He isn't really involved in the main plot but more just background noise. The MV has a bigger take on sequels for the entire series aka the puppet master sorta speak. There is another antagonist but more of a cannon fodder type of villain for the MC in the first book which he interacts with the majority of the time. Just debating to keep the MV in the 1st act as a warm-up for the 2nd book or just take MV out completely just introducing him later on.
The main question you have to ask yourself in this scenario is this: Do you have the MV in the first book just to have a face to an antagonistic force, or is it integral that the MC, or we, know the MV for our understanding of the story? If the story wouldn't change much without the MV being in it, I'd just say take them out and throw them in later.
Not sure how that main villain can work for the first book if he isnt involved in the main plot, but do take him out for the second and come up with another problem for the MC to address.
So maybe you should study how Harry Potter did it. Voldemort is mentioned and hyped up and at the very end makes an appearance, but the "main villain" so to speak was someone else for Book 1, though Voldemort is the main villain for the entire series and obviously acts as the puppet master throughout. Voldemort was never a question mark for the readers, even from the beginning. So maybe look into them
Never read anything about Harry Potter or those books. I had the impression there was just the one villain in your book one which made no sense when he only showed up at the beginning and end. Now if you have a long arc villain then you can't kill him off. But if you also have a main villain for book one he can certainly be eliminated.
There’s the kinda-classic thing of the villain being around as an apparently friendly force all the way through, and then they’re revealed.
You've never read anything about Harry Potter? Of course you have--it's been impossible to avoid. If you haven't read the books themselves, then... maybe you don't need to comment. I think it's a great example to look at, @33percent. You don't want the villain to come out of nowhere when he arrives, but if he's not part of the plot of the first book you don't want him cluttering up the landscape, so... mentions and a brief appearance? Makes sense to me.
I am going to take him out, but use like his henchmen to replace him. Do a build up hype for the 2nd book if there is ever one but the main bad guy is more behind the scenes anyways. Plus I want to create persona mystery about the MV anyways, I do like the Voldemort Approach.
I'd be good if you inserted him like background noise indeed, from my pov. Have others talk about him etc. Make a subtle mystery around him. It works well in trilogies, etc., because it hints that chaos approaches, which is always good to look forward to.