There have been many books written about King Arthur. The question doesn't have enough information to answer properly.
King Arthur
King Harold is the King of medieval Europe in the knights tale
born in 1960 and lived on for many ages
In "The Canterbury Tales" by Chaucer, several characters who are on a pilgrimage take turns telling stories to pass the time. The Wife of Bath's tale takes place in Britain--more specifically, in the court of King Arthur.
The story of King Arthur is a legend or folk tale, and has been written about in many historical novels, films and TV programmes.
the story of king Arthur and Merlin
52 chapters
The legend of King Arthur is a mythological tale, so the idea of his return is not based on historical fact. There is no specific date or event associated with his prophecy.
the lady of the lake appears in many Arthurian Tale: Merlin and King Authur. Her role in both of these stories is basically as the gaurdian of Excalibur until the sword is given to King Arthur.
King Arthur probably was, but legend has twisted the tale of him to make him have a wizard consultor and a dad who fought against magic. Believe what you will.
King Arthur has a son. Different versions of the tale vary, but Sir Thomas Malory's Le Morte D'Arthur, King Arthur has sex with his half-sister (not knowing they are related), who gives birth to Mordred. Mordred is the one who eventually kills Arthur.
No one. There's nothing about King Arthur dreaming, or even falling asleep in the story.