Aporia is an expression of doubt or a place at which a decision must be made.
As Satan addresses his legions in book 1, newly flung into hell, he conveys to them that they are at a juncture or crossroads in which they have to decide what to do. He asks them several questions, such as,
For who can yet beleeve, though after loss,
That all these puissant [powerful] Legions, whose exile
Hath emptied Heav'n, shall fail to re-ascend
Self-rais'd, and repossess thir native seat?
This is not a rhetorical question, though it sounds like one—in other words, Satan here is seriously at a point of doubt or aporia. He is shaken up, and while feeling his legions can fight back somehow, is not sure that a direct assault on God can work. As Satan notes, God showed himself to be wily in the last war:
his strength conceal'd,
Which tempted our attempt, and wrought our fall.
Therefore, Satan is in doubt as to what their next move should be when he asks the question above. He wonders if they shouldn't try a new approach, what he calls "fraud or guile," as he fears "force" will not succeed. We see Satan, in this moment of aporia, thinking aloud. In book 2, the aporia (doubt) continues, with Satan even questioning if concealed war would work, given that God can see everything:
Warr therefore, open or conceal'd, alike
My voice disswades; for what can force or guile
With him, or who deceive his mind, whose eye
Views all things at one view?
In asyndeton, a writer omits conjunctions, such as "and" or "but." In book 2, Satan, as we have noted, is still in a state of aporia as he continues to talk on and on to his evil legions about what they should do to get back at God. He states that he fears a wrong move would really mean their end. He worries that God would win and put them into even a worse position than they are now. He envisions them,
for ever sunk
Under yon boyling Ocean, wrapt in Chains;
There to converse with everlasting groans,
Unrespited, unpitied, unrepreevd
The last three words in the quote above—"Unrespited, unpitied, unrepreevd" are an example of asyndeton. Normally, at the end of a series, one would put the word "and," so that the line would read "Unrespited, unpitied, [and] unrepreevd."