@coggleton I worked through something similar in the trilogy I’m working on now. It’s a quest fantasy, so the problem was that the main protagonist and antagonist were physically separated for the whole first book and almost all of the second. What introduce the backstory of the antagonist which was part of a legend recorded in song in this world. I also gave him very limited telepathic abilities so he could contact my protagonist’s friend. Finally, I’ve given him one POV scene where he receives a vision with cryptic prophecies of the future. Directly, he is not involved in the plot of the first book, but indirectly he has sent a friend of his to stop my protagonist.
Long rant. You don’t have to do it that way. Personally, I think it would be best if you had your main antagonist in right from the start. The coolest idea that’s coming to me at this moment is that maybe in the first book the protagonist thinks he beats the villain, but really the villain is still in control and his plans are much larger than the protagonist realizes.