Sturluson wrote the Prose Edda in the early 1200s to educate readers about Icelandic-Norwegian poetry, which was beginning to die out. There are three sections, the first of which is an overview of Norse mythology, which is essential to understanding the poems and kennings. The second is a fairly exhaustive discussion of how to construct proper kennings, structured as initially as a discussion between Ægir god of the sea and poetic god Bradi but which ends up as lists. The third and final section describes and illustrates thirty different poetic metres, with examples given in the form of poems praising King Hakon and Earl Skuli of Norway.
In the first section, titled Gylfaginning, Snorri integrates the pagan Norse gods into the Christian framework by means of universal history—interpreting them as characters from the Trojan War, who migrated to Scandavian lands and represented themselves as gods. The basic framework of Norse cosmology is sketched by means of a wisdom contest between a wise Swedish king, Gylfi, who was tricked out of some land by the Æsir (Odin and company), and three gods, Three, All-Father, and High (all three are names for Odin). In a wisdom contest the asker (Gylfi) continues asking questions until the answerer cannot answer, but the asker must know the answer to the questions he asks. He starts by asking how the world began, and asking about later and later events. After answering a couple questions about what will happen after Ragnarok, the three tell him that they do not think that he will get any answers (from anyone) if he asks about events after that, and the hall he is in disappears.
The second section, titled Skaldskaparmal, begins with the Æsir entertaining the sea-god Ægis, who gets into a conversation with god of poetry, Bradi, and, apparently having quite a curiosity about poetry, asks Bradi questions and ends up with a very comprehensive understanding of kennings, and a few of the stories that kennings frequently reference. The conversational, question and answer form begins with kennings about the gods, then the goddesses, then important types of people (how to refer to a warrior, a ruler, a wife, etc.), and finally animals.
A kenning is an adjective + noun, which indirectly refers to a different noun in the same category. When referring to one of the gods, or an important person, the adjective refers to something they did. So, for example, Hanged-Tyr and One-eyed Tyr are both kennings for Odin. Tyr is one of the gods, and Odin paid an eye for wisdom, and he hanged himself as a sacrifice to himself. (Tyr seems common to use for Odin, possibly because Tyr is one-handed and Odin had only one eye.) A king is frequently referred to as ring-breaker, gold-hater and the like (a good king is generous, giving away gold, which was often carried as rings). Battles and warriors commonly use kennings, for example, food for Hanged-Tyr’s ravens (a battle), battle-snow (arrows), sword’s tree (warrior). Kennings can also be nested, such as “sea-fire’s hater” (king: sea-fire = gold, gold-hater = king), although not generally beyond four nestings, as it gets pretty difficult to understand.
The third section, Hattatal, is an explanation of thirty different poetic types, each illustrated with a stanzas that together comprise praise poems that Snorri wrote. The base form is called drottkvæt (courtly meter). A stanza has four pairs of lines, each line having six syllables. The first line of the pair has a repeated initial syllable that is the first syllable of the second line. The first line also has a half-rhyme (the rhyming syllable has different initial syllable but same ending syllable), while the second line has a full-rhyme (the rhyming syllable has the same initial vowel and following consonants). The first rhyme is at the beginning of the line, while the second rhyme is the penultimate syllable of the rhyme. Snorri gives the example:
Læt-r sa-r Hakun heitir
hann rekkir lid bannat
iörd kann freesia fyrdum
fridrofs konung-r ofsa
Sialf-r ræd-r allt ok Elfar
ung-r stiller sa milli
gram-r a gift at fremir
Gandvik-r iöfur-r landi
The other poetic forms vary the number of syllables in a line, after the second rhyme, whether the rhymes are half or full, etc. There are also variations that use drottkvæt, but use different qualities of kennings (poetic kennings that are described, or allusive kennings like described above) and locations of kennings.
Since formal poetry requires both rhymes and alliterations, kennings are useful in being able to communicate a concept with many possible syllables. Kennings are, of course, poetic in nature themselves, and thus are naturally used in poetry. In fact, much poetry, even non-Icelandic poetry, uses a sort of descriptive kenning which alludes to what is being described. “The fog comes on little cat feet” is not dissimilar to “The noble king poured out much mead for the hearth-watcher [wolf; wolf’s mead = blood; poured out blood = fought a battle, spilling his enemies’ blood]”. Although “on little cat feet” is more correctly a metaphor, one could consider it to be a modern, atypical, kenning for “silently”.
The cosmology frequently cites the poem Voluspa and is somewhat contradictory. For instance, the All-father is one of the names of the god that created everything, but that is a name of Odin, who was a descendent of the god who killed Ymir. At other times it seems that nobody created: Ymir and his cow came into being from melting droplets of Niflheim (melted by the heat from Muspell). Likewise, Niflheim and Muspell are clearly not terrestrial locations (since the heavens were created from Ymir’s skull and the earth from his body, after one of his descendants killed him), yet Muspell is described as being south and Niflheim as being in the north.
The Prose Edda is clearly a source for a lot of fantasy. This is most notable is Tolkien, which is a remix of Scandavian and Anglo-Saxon literature. Dwarves live in the earth and a craftsmen; they make Thor’s hammer, and a large ship that can fold up to a small size, among other marvels. It seems like Tolkien’s elves are a combination of the Edda’s elves, who live in the third heaven, and the Æsir: the god’s like the elves, are powerful, but can be killed. The elves, like the gods and any nobleman, have poetry and songs for entertainment at a feast. The elves’ poetry is concerned with family lineages and lauding the famous deeds of people, as is much of norse poetry. Tolkien’s poems even have elements from Snorri’s poetic forms, although more frequently they combine Anglo-Saxon alliteration with English rhyme. Just like Norse objects, especially well-crafted objects or historically important objects have names, such the elf-swords Bilbo’s party finds, as well as Aragorn’s sword. Even referring to the proximate rulers of the world as a group with Norse-sound name (Valar) is reminiscent of the Æsir and Vanir.
Other elements influence fantasy in mining pieces of the Edda. The dark-elves of fantasy computer games come from one brief mention in the Edda, although the context suggests that dark elves are dwarves, not evil elves. It is hard not to see Snorri’s list of synonyms and kenning-components for common animals and objects as part of the inspiration for the list of true names that wizards memorize in A Wizard of Earthsea (although true names does not seem to be part of Norse thinking). Speaking someone’s name as a way of summoning them is probably wider than just Norse culture, but there is one time when Thor was a way and the Æsir urgently needed him; one of them speaks his name and he appears. This is used in The Forgotten Beasts of Eld, and in the negative in being forbidden to speak Voldemort’s name (and when they do, it effectively summons Voldemort’s enforcers).
Snorri’s Prose Edda is interesting and inspiring reading. It is not only our most complete source of Norse cosmology, but it also is part of the source material for high fantasy (even if sometimes only through Tolkien). Since about half of it is poetic source material, it is easy to get inspired to write poetry and use kennings, like Tolkien obviously was. If you are looking for storytelling, Neil Gaiman’s Norse Mythology fleshes out the narratives and makes for more interesting reading. However, if you are interested in writing fantasy, especially anything remotely resembling Tolkien, this is required reading. Likewise, it is helpful to read this first before reading the Poetic Edda.