Was The Beginning/Dominion intended to be duology ?

"Dominion" was actually filmed first. However, the studio HATED it and found it not commercially viable at all. So, they scrapped it and reshot the whole movie over (using very little of the same cast), which was "The Beginning". This is the version they released in theaters. They later gave "Dominion" a brief, limited release when fans clamoured for it.

I saw BOTH in the theater (and ended up buying both on DVD as I am a fan of the series), but I did NOT like either film. Of the two versions, I agree that "Beginning" was the more commercial film and that was the right choice to release widely in theaters. But I still thought it was BAD. It started off well enough and just disintegrated. The whole ending with (**spoiler**) Father Merrin chasing the possessed woman through the caves while she had the SAME possessed face as Linda Blair was incredible idiotic. And that was just the tip of what was wrong with the movie.

"Dominion", while more cerebral, was flat out dull. I drove 3 hours away to see this film in the theater, dragging a friend along with me. We were bored to tears. There was ONE other person in the audience and he was SNORING. Literally.

"Dominion"'s box office was non-existent for the most part. "The Beginning" made a few million, but NOT nearly enough to cover the expenses of filming BOTH versions of "Part 4". Together, these were the biggest box office flops of the whole series. There have not been any further sequels, but there has been talk of a remake of the original and, at one time was discussion of a TV series or mini-series remake. We'll have to see what happens. For now though, I think the original series is DEAD. (Which is disappointing, because I generally like the series--but both versions of "Part 4", in my opinion, are just awful).

Just mistakes, I think. Having a whole series of films in which Father Merrin became a globe-trotting demon-buster before 1973 wasn't an idea in anyone's minds, I'm pretty sure.