1980 novel by Mary Stewart, the last book in her Merlin Trilogy, a retelling of the Arthurian legend (see Arthurian Mythology and The Chronicles of King Arthur) from the magician Merlin's point of view.
The sequel to The Crystal Cave and The Hollow Hills was written to stand on its own but picks up immediately where its predecessor left off---the young King Arthur has just been recognized rightful High King of Britain by its lesser kings and nobles, thanks to the miracle of his raising the sword Caliburn (Excalibur) from a stone altar (see The Sword in the Stone). Arthur's father, Uther Pendragon, died shortly after naming his heir, who had been raised away from court due to the scandalous circumstances surrounding his conception. As a result, the kingdom was in some dispute, but the raising of Caliburn dispelled even the challenge of King Lot of Lothian. All this is recounted briefly in the opening chapter, having been told in great detail in The Hollow Hills.
The Last Enchantment refers to the fading of Merlin's power with old age. Although he still possesses the Sight that was the key to his early exploits, the magician is no longer a conduit for divine intervention among Britain's royalty. Still, he designs the royal city at Camelot, serves as Arthur's chief advisor, confidant, and friend, and the legends of his magic (which he explains even while relating the actual events according to Stewart's interpretation) are still powerful. He even trains a replacement: Nimue, who came to him disguised as the boy Ninian in the hopes of fulfilling her dreams of magic. In The Last Enchantment she is Merlin's partner and lover, and although she does seal him in the hollow hill at his death, it is due to the treachery of another woman, Lot's queen Morgause, half-sister and seductress of Arthur, that she does so. When Merlin escapes from the crystal cave, having recovered from the deathlike sickness brought on by Morgause's poison, he lets Nimue, who has become the Lady of the Lake, continue in his role of King's magician and advisor, which she has aptly filled. The novel concludes with Merlin easing his way into retirement, confident of the future.
Although The Last Enchantment, like the rest of The Merlin Trilogy, contains the seeds of the tragic conclusion of the Arthurian saga, the disasters that fell Camelot are left for another book---The Wicked Day, narrated by Arthur's son and nephew by incest with Morgause, Mordred.