Paradise Lost

The lines in your question are especially significant in John Milton’s epic Paradise Lost (first published in 1667) because they belong in a passage that introduces firsthand the epic’s villain, Satan.

Before this passage, Milton has told the reader about the heavenly war that led to Satan's ousting from heaven, but now we get a glimpse of Satan himself and hear him speak as he lies in a fiery lake in Hell. Satan is indeed chained to the lake, as explicitly mentioned in a later line from the passage:

So stretcht out huge in length the Arch-fiend lay
Chain'd on the burning Lake

But even before the introduction of this line, we can infer Satan is confined to the lake since he lies “prone on the flood.” The flood is fiery since God has flung Satan and his hordes to this new place, Hell, as a punishment. Thus, this passage conveys a sense of the enormity of Satan’s crime (and punishment), as well as his literal, physical might. An interesting question that arises here is, why do these lines show Satan to be so physically mighty?

As you can see, the description positions Satan as a larger-than-life figure in the epic. Through imagery, allusions, metaphors, and other rich poetic devices, Milton presents a rather impressive Satan. In a startling nautical metaphor, Satan is compared the Biblical sea-beast “Leviathan,” which is often described as a gigantic serpent. He is then conflated with a whale against whom the pilot of a lost ship drops anchor, assuming it to be an island. In allusions to Greek and Roman myths, Satan is also identified with the fallen Titans whom the Olympian Gods defeated, as well as the Typhon, an enormous, deadly serpentine giant. Further, Satan's size is suggested to be many a “rood,” a measure that denotes six to eight yards. Descriptions such as these and Satan’s larger-than-life speeches in books 1 and 2 are what led some critics, especially the romantic poets, to describe Satan as a “heroic” or tragic figure.

However, this view has long since been discarded. Milton was a Puritan who strictly wrote Paradise Lost as a Christian epic in which Satan is the absolute villain. Satan’s character grows more negative after book 4 and especially in Paradise Regained. Further, Satan’s showy, rebellious glamour may appeal to modern readers, but Milton as a Puritan would have disliked flashiness.

Thus, in painting Satan as a larger-than-like figure, Milton may have actually been underscoring his unpredictability as well as his dangerous appeal for humanity. Another significant reason why Satan is compared to gigantic, though dangerous, figures in the passage we are discussing is that Milton wants to convey the vast scope of the threat Satan represents, as well as prove God’s might: if his very adversary is so powerful, how immense would God’s power be? Moreover, just like the “seaman” in line 205 mistakenly sinks his anchor in the scaly side of the whale, humanity too could be deceived by Satan. This foreshadows Satan’s seduction of Eve in Paradise. Finally, the weird, wonderful conflation of ancient allusions with practical, nautical imagery is both an excellent example of Milton’s use of a conceit, a metaphor that compares two very different things, as well as a dark reminder of Satan’s ever-present threat.

This passage sets the scene for the beginning of the main body of Paradise Lost. After invoking the muse (reminiscent of older epics), explaining his purpose, and giving a brief summary of the war between Lucifer's rebellious angels and heaven, this description set up the beginning of the work's first actual dialogue.

While the immediately surrounding passages more directly highlight the aspect of Satan being punished, this is a description of him at the Lake of Fire, a location that is fundamentally associated with him being punished.

In Paradise Lost, it is clear that Milton is seeking to create an epic within the Christian mythos that parallels the great Greco-Roman epics. The host of allusions in this passage, building off of the invocation of the muse and the in media res beginning, all add to this effect.

The reference to Norway is noteworthy in helping to set the work in the geography surrounding England. By combining the host of Greco-Roman references, biblical references, and these kinds of details, Milton sets up his work to connect to both the classics and an immediate and modern context.

This passage is from Book I of Paradise Lost which begins in media res as do the Greek classics after a brief proposal of Man's disobedience and the loss of the paradise of Eden, with the mention of the cause of this loss as the temptation of the Serpent, or Satan. The cited passage begins with line 195, directly after Lucifer, which means "light-bearer" is cast out after being "Stirr' up with Envy and Revenge" and becomes Satan, which means "enemy." Satan awakens from confusion and stirs his "Rebel Angels" who are also confounded by their predicament as they find themselves chained on the burning lake of Hell (see line 210).Here are some of the literary elements of the above passage:

Classical Allusions

Lines 195-208) allude to the classics. For instance, the reference to Titan recalls the war of the Titans with the gods of Olympia. Briareos helped to defeat his brother Titans; the reference to Typhon is found in Hesiod's story in which Typhoeus is a most frightening Earth-born monster whom Zeus hurled back from Olympus. Ovid's described him as having been buried alive under Aetna and nearby mountains. Further, the allusion to Leviathan has several references, many scholars believe that it is nearest to the Isaiah's prophecy that the Lord

...shall punish Leviathan, the piercing serpent...that crooked serpent; and he shall slay the dragon that is in the sea.

Themes

Certainly, the themes of the essential importance of obedience to God and the Nature of the Universe as a Hierarchy are prevalent in this passage.

Satan and his legions have been chained on the burning Lake for their disobedience, while it is apparent from the allusions to the classical war of the Titans that there is an order of being.

Simile

This passage contains an epic simile as Satan is compared to the giants of classical literature. With such a grand comparison, there is, indeed, the suggestion of the puissance of Satan and his Legions, the arrogance and pride that will drive the devils to "find means of evil."

Personification

Night, Sea, and Morn are all invested with characteristics of humans in lines 206-207:

...while Night
Invests the Sea, and wished Morn delays.

Poetic Devices

With enjambment, the continuation of a sentence or a clause over a line break--

e.g.

Leviathan, which God of all his works
Created hugest that swim th'Ocean stream"

and with caesura, or variable line lengths--

e.g. 

With fixed Anchor in his scaly rind
Moors by his side under the Lee,while Night

Milton creates other audible interests for readers, as well, such as with inverted sentences. Two sound devices that the great poet employs are assonance and alliteration. There is assonance, the repetition of a vowel sound of the o:"Prone on the Flood, extended long and large (line 195)"; alliteration with the repetition of an initial consonant sound of the letter l: "long, large" and in line 204 with /s/: "The Pilot of some small night-founder'd Skiff."