After passing through the gates of Hell, Satan makes his arduous ascent through Chaos towards Earth:
So eagerly the fiend Ore bog or steep, through strait, rough, dense, or rare, With head, hands, wings, or feet pursues his way, And swims or sinks, or wades, or creeps, or flyes:(II. 947-50).
I read "eagerly the fiend" as a dactyl (one stressed syllable followed by two unstressed) followed by an iamb, making the last few words of this line trip along quite quickly, reflecting Satan's eagerness to move onwards and upwards. But the rhythm of the next line confounds his eagerness, as three iambs are followed by a spondee ("rough, dense") that disrupts the standard iambic march forward through the line. Milton does the same thing in the next line, this time trading out the second iamb for a spondee ("hands, wings") giving us an extra stressed syllable to stumble over. The following line returns to uninterrupted iambic pentameter, but the repeated "or" turns the line into an obstacle course, as the reader must repeatedly clamber over the conjunction in order to get to the next verb. Thus the metre helps us to experience how Satan's lively eagerness to move forward swiftly is disrupted and frustrated by the warring elements of Chaos.
Milton also plays with ambiguity in the vocabulary of the passage. In the second line of the quoted passage, we have "bog" set next to "steep." The meaning of "bog" is clear enough, but "steep" can mean a mountain or precipice (in which case it stands in contrast to the low "bog") or can also suggest the process of steeping, or soaking (in which case it corresponds to "bog"). Additionally, according to the OED, Milton often uses "steep" as an adjective indicating difficulty or insurmountability as when, in Areopagitica, he refers to "a steepe disadvantage of tyranny and superstition."
The sequence, "strait, rough, dense, or rare," creates further problems, because this is a list of items through which Satan is supposed to be moving, yet the third and fourth item in the list are adjectives (the first two could be adjectives or nouns). So what appears initially to be a list of geographic features (a narrow passage and rough terrain) transforms mid-line into a list of qualities possessed (presumably) by the matter around Satan. But where is the noun that the adjectives modify? And in what sense are we now to take "strait" and "rough"? Milton quite rightly does not give us a clear and coherent picture of Chaos. The next line of verse continues to offer us the disturbing sensation of traveling through Chaos as we see Satan making his awkward way between worlds. Here we do not see the fallen angel in his entirety, but rather as a jumbled collection of parts, almost as if he is himself coming apart amongst the warring, fragmentary elements.
Milton creates a similar effect in a passage in Book III. In the course of heaping derision upon Catholics, he describes how the souls of some deluded worshippers float up towards Heaven, through the various celestial spheres, almost to the Pearly Gates themselves,
when loe A violent cross wind from either Coast Blows them transverse ten thousand Leagues awry Into the devious Air; then might ye see Cowles, Hoods and Habits with thir wearers tost And flutterd into Raggs, then Reliques, Beads, Indulgences, Dispenses, Pardons, Bulls, The sport of Winds:all these upwhirld aloft Fly o're the backside of the World farr off Into a Limbo large and broad(III. 486-95).
Although Milton doesn't manipulate the metre of these lines as he does in the previous passage, he still manages to create a similar effect in the the list of Catholic accoutrements: "Reliques, Beads, / Indulgences, Dispenses, Pardons, Bulls." The absence of conjunctions (asyndeton, for you rhetoricians out there) creates an effect of disorganization and distress. In this arrangement, the sacred Catholic objects become an undignified and insignificant mass of insignificant items, fit to become the trivial "sport of Winds." Furthermore, the Catholic souls that have been caught in the cosmic wind are reduced not to their component body parts (like Satan) but instead to bits and pieces of clothing: "Cowles, Hoods and Habits." Milton, significantly, has only moments earlier complained about people who don supposedly sacred clothes but who do not posess true faith:
And they who to be sure of Paradise Dying put on the weeds of Dominic, Or in Franciscan think to pass disguis'd(III. 477-80).
Such a feeble, false piety cannot deceive the heavenly wind, which reveals the insubstantiality of these foolish souls, reducing them to mere shreds and patches before blowing them off to an eternity in Limbo. In Milton's universe, this is what happens to the undeserving (i.e. Catholics) who attempt to ascend to heaven. Satan, also attempting an illegitimate ascent, suffers a similar, although temporary, dissolution.