What four "phases" does the court of Camelot go through?
The four phases of Camelot correspond to the four sections of the book.
"The Sword in the Stone" is probably the best known section of the book, having been made into movies Disney cartoons. It is the phase that deals with Arthur's childhood. This is a magical time when he is being tutored by Merlin. Arthur does not yet know who his parents are or what his destiny will be until he pulls the sword from the stone.
In the second section, "The Queen of Air and Darkness," Arthur learns that he has a sister, Morgause. Using magic, she seduces Arthur and conceives a son, Mordred. Arthur also establishes the round table.
"The Ill-Made Knight" is Lancelot. He falls madly in love with Arthur's wife and tries to fight those feelings. Arthur also devises the quest for the Holy Grail for his knights. Lancelot is the ill-made knight because of his passions, and he is not worthy of the grail.
"The Candle in the Wind" is the final phase of Camelot. Arthur has to deal with Mordred's treachery, Lancelot and Guenevere's betrayal, and his own downfall. When he dies on the battlefield, his body is transported to the isle of Avalon.