The Nibelungenlied, an epic poem of German literature, is a conflation of three thirteenth-century manuscripts by an anonymous Austrian author. It tells the tale of the courtship of the Burgundian princess Kriemhild by the heroic warrior Siegfried, a prince from the lower Rhine. When his entanglement in the affairs of her brother, King Gunther, results in the prince's death, his bereaved beloved vows her revenge.

It would be impossible to describe the Nibelungenlied as teaching a "moral lesson" in the way that phrase is usually understood. Despite appearing at a time when the literature of England, France, and Italy were suffused with the influence of Christianity, the characters of this tragic epic seem to spring from a much harsher pre-Christian, or even Homeric, world. If the wrath of Achilles is the theme of the Iliad, the revenge of Kriemhild is its formidable counterpart here. Rather than a moral framework, it might be more accurate to say that the Nibelungenlied is ruled by an ethos of vassalage, a warrior's code of loyalty in a feudal society. And in the terrible and violent absurdity of its conclusion, it lacks even the rough justice of the Greek world and seems much closer in spirit to our own.

The poem "does not have a clearly-defined moral message for the reader. However, it raises important questions about the nature of loyalty, honor, and what constitutes tragedy."

For example, loyalty and honor were entwined with the notion of chivalry, which "encouraged knights to foster the virtues of courage, honor, and service to their lord or kinsmen. Part of this code prescribed respectful treatment of women, who had few legal rights in the Middle Ages."  Honor was also enmeshed with the notion of courtly love:  "the suitor always treated his lady with respect and admiration, sometimes even adoration. An example of courtly love in the Nibelungenlied is Siegfried's unspoken devotion to Kriemhild and then his respectful wooing of her through Gunther over more than a year."

In order to understand how loyalty, honor, and tragedy contribute to the sense of morality, I encourage you to visit the link below here at eNotes that addresses these themes.