Focus on these lines - why are they significant? What do they reveal?

book 4

Focus on these lines - why are they significant? What do they reveal?

Now rowling, boiles in his tumultuous brest,
And like a devillish Engine back recoiles
Upon himself, horror and doubt distract
His troubl'd thoughts, and from the bottom stirr
The Hell within him, for within him Hell [ 20 ]
He brings, and round about him, nor from Hell
One step no more then from himself can fly
By change of place: Now conscience wakes despair
That slumberd, wakes the bitter memorie
Of what he was, what is, and what must be [ 25 ]
Worse; of worse deeds worse sufferings must ensue