I'm personally really big on taking a Jungian filter to all story writing ad reading--including to the Bible itself. That means we need to be clear about who is in control, and who is top dog, and who bows down to whom.
From what I'm reading in your description, the witch is the chief bad guy, and anyone called a "henchman" would be her servant or her toady. So, is this a case of the Devil only temporarily PRETENDING he is weaker than the witch, and so he's conveniently hiding himself in the guise of a mere lowly henchman to her, when his true plan is to reveal himself as the all-powerful Satan at a later date of his choosing?
The Devil (ARgus) acts like her henchman/lover, but he's really working behind her back to take over the land, like a chess game. It's really, well, scary b/c he just kinda took over his own character. Weird.
I think the correct dynamic between the witch and her "henchman" needs to be clarified here. Who is in control? By grapsing that we can "enjoy" the villain more.
One of the things we all love about a villain is the enjoyment we get from HATING that villain. And our ability to hate--and our enjoyment of that hate--is directly linked to our understanding of how much power the villain has (here's where the Jungian filter comes in handy). Any villain's power, and the sordid details concerning his abuse of that power, needs to be made clear to us so we can hate him for it and enjoy watching when the time finally comes for his power to be taken from him.
Cool!!!
So .... can you clarify why he chose to hide himself as a henchman?
mmm . . . I'll get back to you on that one. Good question!!!!!
Are you planning to turn the tables so that we at first hate the witch and that we mistakenly believe SHE is the top dog, but then we feel sorry for her later when the true master of evil is revealed?
Yes.
Will the witch get redeemed later?
Yes.
At what point do we learn that HE is the one holding all the cards, and so the witch has been deluded and is his unknowing puppet? At what point do we figure out that he is Satan (or is that left vague and we just kinda have to attribute that to him on our own)?
Towards the end of the story.
Villains are never flat if we understand the power that they hold. So I need to understand this villain's power, how he wields it, what his MO is, what his weaknesses are, etc.
mmmm . . . . good. weaknesses, powers, how he wields it, mo. mmm . . . devil has lot's of weaknesses. man, you've given me a lot to think about.
If his MO is that he has come to "kill, steal and destroy" and if his standard tools include lies and deception (including deceiving the witch) then help us focus on his utter depravity.
ooo . . . . I like. Ok, juices are running. Must go write now. Can not turn away from PC. Going down now.
And here's a possibility: foil the witch's "style" of evil against the Devil's. To explain .... Perhaps the witch is a bit on the freaky/maniacal side (in other words, maybe she's one of those out-of-control types always in a frenzy) and the Devil is icy calm, and thus a total foil to her. So, when the tables ARE turned on her, it's all the scarier that this icy calm henchman of hers takes over. If you foil her personality against his via that sort of contrast of crazy vs. calm, that can help delineate his personality for us via the comparison.
Um, when did you slip into my PC and read my story? LOL!! This is what happens.
Other stories with two bad guys have done this sort of contrast to great effect. The original "Die Hard" movie had the icy calm Franz who was the intelectually calm and cold mastermind of the robbery, and he was foiled against the psycho blond German guy whose brother was killed by Bruce Willis, and so he swore to get psycho vengeance upon Willis.
I don't know if you've gone for this sort of a dual bad guy scenario with one being a maniacal psycho and one being icy calm, but if you have, foiling them one against the other can be used to great effect in bringing out their personalities.