Honor
Most of the tension in the saga comes from one principle: retaining honor. Many vengeful killings occur throughout the saga, but in order to retain honor during those trying times, the killer must either pay the kinsmen of the deceased or prepare to lose one of his own kinsmen to blood vengeance. In the name of civilized society, the payments should theoretically deter blood vengeance from occurring at all, but that is simply too hard to bear for most of these warriors. They would much rather act on their anger, as is the natural response. To accept payment or to accept self-judgment—a practice in which the kinsman of the deceased allows the killer to determine his own punishment/payment—is the honorable act. Gunnar, the reluctant killer, demonstrates a high level of honor throughout the saga, until the very end when he goes back on his promise to fulfill his punishment of temporary exile. Fittingly, he is killed as a result of this breach of honor.
Masculinity
Masculinity is the bane of honor because it fuels blood vengeance. We can look at Bjorn the White, a man who seeks to increase both his masculinity and honor by accompanying Kari on his quest for justified blood vengeance, as an example. His wife asserts that if he fails to perform as a warrior, she will never let him in their bed again. Indeed these two aspects of medieval Icelandic life, fighting and reproducing, are entangled with masculinity. Hallgerd is attracted to Gunnar precisely because he has demonstrated his masculinity through raids and physical prowess. If a man is seen crying at any time, his masculinity is immediately questioned. Many shameless characters lie about whether a man has wept in order to jeer them into action. Njal's inability to grow a beard is also the subject of masculinity-diminishing jokes. Perhaps the most masculine act in the entire saga occurs when Thorhall Asgrimsson learns of the burning of Njal. He withholds tears, but cannot help but demonstrating his grief: blood comes spilling out of each ear. He stands up immediately to say that this was not a very masculine thing of him to do—but it definitely was.
Christianity v. Paganism
The conflict between these two religions comes up quickly and is settled rather quickly as well, though its effects are lasting. Njal is seen as a wise character long before the advent of the new religion, so when he is among the first to pick it up, it seems to be painted as the 'correct' religion in some ways as well. Because Gunnar's death takes place in a pagan Iceland and Njal's takes place in Christian Iceland, we can glean a lot about how these two religions were perceived through the associated symbols therein.
Gunnar is heard reciting poetry from his grave, sitting up, while Njal is found basically unburned and even glowing. There is a spiritual power to both religions as demonstrated by the manifest pagan curses throughout the saga, including the black fog toward the beginning, the earth-splitting chasm curse in the middle, and the witch-ride toward the end. Aside from Njal's early adoption, the saga only seems to assert that Christianity wins out in the end through legal process. The significance of this religious conflict seems to be in its immense power to divide people, as any reader can see by taking a look at modern politics, wars, and really any other time throughout history. After the Battle of Clontarf, a conflict between the Christian King and pagan viking forces, and the extended results of Valgard's pagan curses on Mord's holy objects resulting in the blood vengeance that takes up the entirety of the second half of the saga, we can see that the battle between the religions had a much larger impact than the initial legal announcement declaring Christianity the winner.
The Law
The saga pays very close attention to the details of the law, and the top lawyers in Iceland are all considered honorable men. However, the law is in direct conflict with man's natural brutality and desire to take revenge. The fact that an annual gathering of all the free men in Iceland is centered on legal proceedings gives hope to the future of the law in Iceland, but even the appeals court can't save them from breaking into an all-out battle when deception and trickery is brought into the proceedings, a not uncommon tactic in medieval (and, sadly, modern) law.
Fostering
Many characters have bonds with their foster-fathers or foster-sons that are even stronger than their relationships with their biological parents and children. Njal taught one of his foster-sons in the law, and this foster-son became the best lawyer in all of Iceland. His other foster-son, Hoskuld Thrainsson, was slain by his own sons, and Njal said that he would rather give up all his biological children for Hoskuld to still be alive. In that particular case, Njal fostering Hoskuld Thrainsson was also a way to make further peace after the killing of Thrain. Unlike in modern times, a person does not need to lose a parent to also gain a foster-parent. This peculiar institution seems particular to medieval Iceland, but may be represented in other cultures as well in the forms of apprenticeships and youth ministries.
Kinship
Being a kinsman with confrontational or otherwise battle-oriented persons can be a serious liability, as we see throughout the saga. Not only is there the burden of pursuing blood vengeance, but also the confronting of killers and asking for compensation, which must be a terrifying task depending on the killer. Legal settlements, such as the many between Gunnar and Njal, demonstrate that it takes extraordinary men to overcome the vengeful ties of kinship in favor of clemency. Kinship also makes Mord Valgardsson pursue the case that he instigated in the first place because his wife's father has the power to take her away from him if he does not. The jury is still out on whether kinship is a blessing or a burden in medieval Iceland.
Exile
One of the alternatives to pecuniary compensation or blood vengeance is a sentence of exile. In the saga, there are two versions of this punishment: lesser and greater outlawry. The former is a three-year banishment that allows the subject help on his way out of the country and a stipend for his family, who may continue to maintain his land. The latter is a lifetime exile, and no help may be given to the defendant. In fact, he can even be killed without redress on his way out of the land. When Flosi and the burners receive their sentences, Flosi—the leader of the pack—receives the lesser sentence while the rest are banished for life. While this may seem backwards, Flosi did have a greater claim to the blood vengeance of the burning than the others in medieval Iceland's social traditions.
