In "Morte d'Arthur," the black hoods worn by Lancelot and his knights symbolize mourning and penance for their sins. They also signify a desire for anonymity and repentance for their past actions, particularly in the context of the tragic events unfolding in Camelot.
Which battle? There are dozens of battles in the Morte d'Arthur.
Throw Excalibur back to the lady of the lake.
Malory foreshadows Arthur's death in "Le Morte d'Arthur" with the title of the story. The title is French for "The Death of Arthur."
MAIN: arthur, lancelot, Merlin and also Gawain
That means "the death of Arthur".
Tragic. informative.
Arthur calls off the siege of Benwick and returns to Britain because news of Mordred's rebellion and Queen Guinevere's affair with Lancelot reaches him. He realizes he must return to Britain to deal with these threats to his kingdom and honor.
I think it represents there being no where to rest and an overturn of hierarchy, but it is for you to interpret how you want.
the hermit who buries King arthur was once the Bishop of Canterbury
The part of "Morte d'Arthur" that involves an element of the supernatural is when King Arthur is taken to Avalon by the sorceress Morgan le Fay after being wounded in battle. This mystical realm is where Arthur is said to rest until he is needed again.
Sir Mordred stabs Arthur in the head during their battle in "Le Morte D' Arthur". The wound is fatal, and Arthur presumably passes away a short while later.