The mood of individual stories in the book tends to be celebratory. Arthur's knights usually win their battles and accomplish what they set out to do. For example, in Book 5, Arthur and his knights pull off a stunning win against Emperor Lucius and 100,000 men. And although not everyone manages to find the Sangreal, Galahad, Percivale, and Sir Bors work together to successfully fulfill Merlin's prophecy that Galahad would be pure enough to achieve it. The knights' regular gathering for the Pentecost feast gives them and the reader a chance to reflect on and celebrate the knights' impressive achievements thus far.
Throughout all of this celebration, the reader also feels suspense over when the mood is going to shift. The book is called Le Morte D'Arthur, or the Death of Arthur. Even as the knights of the Round Table are winning their battles, then, there is a sense that it must all come to an end by the time the reader finishes the book: the more battles won, the closer the Round Table is to breaking. Ominous dream-visions that the knights struggle to fully interpret contribute to the suspense.
By the last few Books, the mood shifts considerably toward tragedy. Civil war breaks out among Arthur, Launcelot, and the other knights of the Round Table. Whereas the knights have fought amongst themselves before, this fight is bigger than ever before. It does not just break out between two main people, but rather causes whole factions to form. The narrator begins to more frequently allude to the time after King Arthur. For example, in Volume 2, Book 21, Chapter 3, the narrator describes a treaty with Mordred:
So then they departed, and came to Sir Mordred, where he had a grim host of an hundred thousand men. And there they entreated Sir Mordred long time; and at the last Sir Mordred was agreed for to have Cornwall and Kent, by Arthur’s days; after, all England, after the days of King Arthur.
The phrase "after the days of King Arthur" forces the reader to confront that the glorious time Malory has been describing is coming to a close. If the loss of Arthur himself were not tragic enough, the treaty installs Mordred, a villain, in Arthur's place. The reader, who lives "after the days of King Arthur," gets the sense that they have inherited not Arthur's magical kingdom, but rather a spoiled political world. It is actually Constantine who eventually replaces Arthur, but it hardly matters. Malory has already made the reader feel mournful about what the world has lost with Arthur's death.
