On using "in it" in a sentence

Question

The phrase in it does not sound familiar to me, but I might be wrong.

The XXX is the most critical part of our work. In it, [description]

Does in it sound correct?

Answer 1

Here examples from literature (many sources, so without links):

“In it?”
“In it, that is.
In it, he found this.”
In it was a table, a long one.
In it, rather.”
“In it, my lady.”
In it was a silver key.
In it I see my fellow-
In it were papers.
In it the dreams that appeared in his mind were seen with two good eyes, not just the half-view of one.
In it was a cell phone I didn't recognize.
In it there’s the number of that old man’s car and a note of explanation for the Captain.”
In it could be no freedom.
In it, I had just turned back and wore a look of shock on my face, but most of my body was clearly exposed.
In it I saw Savannah, sitting up, rubbing the back of her head, Lucas and Paige crouched beside her.
In it was a photograph taken of me on our wedding day.
In it, a pointed black stone with red veins hung from a think leather cord.
In it was my ticket for the next bus.
In it, she was bent over the altar as she was now, with her hands pressed flat, as they were now.
In it there were two straight-backed chairs, one table, one robot, and one policeman.
In it, I have asked him for temporary powers here in Deal.
In it resolved a woman’s face.
In it violet, yellow, and red beams swirled from above.

So, now I think this is sound naturally!

Answer 2

It is correct. For example:

The first chapter is the most critical part of our work. In it, [description]

In this example, the pronoun "it" refers to the first chapter of the work. The description will then go on to explain what the first chapter contains. In other words, what is in it.

Answer 3

I would rather recommand the use of "In this part / section / module / etc.".

Using "in it" is more common when the "it" has already been mentioned in the sentence, like "My fridge has some oranges in it".