Robert de Boron in the context of Lancelot–Grail

Merlin (Welsh: Myrddin, Cornish: Merdhyn, Breton: Merzhin) is a mythical figure prominently featured in the legend of King Arthur and best known as a magician, along with several other main roles. The familiar depiction of Merlin, based on an amalgamation of historical and legendary figures, was introduced by the 12th-century Catholic cleric Geoffrey of Monmouth and then built on by the French poet Robert de Boron and prose successors in the 13th century. Geoffrey’s account presented Merlin as both a prophet and royal advisor.

Geoffrey seems to have combined earlier Welsh tales of Myrddin and Ambrosius, two legendary Briton prophets with no connection to Arthur, to form the composite figure that he called Merlinus Ambrosius. His rendering of the character became immediately popular, especially in Wales. Later chronicle and romance writers in France and elsewhere expanded the account to produce a more full, multifaceted character, creating one of the most important figures in the imagination and literature of the Middle Ages.

The Lancelot-Grail Cycle, also known as the Vulgate Cycle or the Pseudo-Map Cycle, is an influential 13th-century French Arthurian literary cycle of unknown authorship written in Old French. Consisting of a series of interconnected prose episodes, it is a lengthy faux chronicle-style chivalric romance that retells the legend of King Arthur while focusing on the character of Merlin, the love affair between Lancelot and Guinevere, and the religious quest for the Holy Grail. Expanding on Robert de Boron's "Little Grail Cycle" and the poems of Chrétien de Troyes, the work ties their previously unrelated and disparate stories together into a coherent single tale and supplements them with new material, such as additional details, original characters, and side stories. It also features an ending inspired by the Arthurian chronicle tradition by Geoffrey of Monmouth.

There is no unity of time and place within the plot, but most of the episodes take place in Arthur's British kingdom of Logres. One of the main characters is Arthur, around whom gravitates many other heroes, including the Knights of the Round Table. The chief of them is Lancelot, whose chivalric tale is centered around his illicit romance with Arthur's wife, Queen Guinevere. However, the cycle also tells of adventures of a more spiritual type, featuring the Round Table's search for the Holy Grail (the vessel that contained the blood of Christ), until Lancelot's son Galahad ultimately retrieves it. Other major plot-lines include the accounts of the life of Merlin and of the rise and fall of Arthur.

Excalibur is the mythical sword of King Arthur that may possess magical powers or be associated with the rightful sovereignty of Britain. Its first reliably datable appearance is found in Geoffrey of Monmouth's Historia Regum Britanniae. Excalibur as the "sword in the stone" functioning as the proof of Arthur's lineage is an iconic motif featured throughout most works dealing with Arthur's youth since its introduction in Robert de Boron's Merlin. The sword given to the young Arthur by the Lady of the Lake in the tradition that began soon afterwards with the Post-Vulgate Cycle is not the same weapon, but in Le Morte d'Arthur both of them share the name of Excalibur. Several similar swords and other weapons also appear within Arthurian texts, as well as in other legends.

Sir Perceval of Galles is a Middle English Arthurian verse romance whose protagonist, Sir Perceval (Percival), first appeared in medieval literature in Chrétien de Troyes' final poem, the 12th-century Old French Conte del Graal, well over one hundred years before the composition of this work. Sir Perceval of Galles was probably written in the northeast Midlands of England in the early 14th century, and tells a markedly different story to either Chretien's tale or to Robert de Boron's early 13th-century Perceval. Found in only a single manuscript, and told with a comic liveliness, it omits any mention of a graal or a Grail.

Beginning in a similar vein to Chretien's story of a boy brought up in the forest by his mother, who comes naively to King Arthur's court seeking knighthood then wanders out again into the forest wearing the armour of the Red Knight whom he has just killed, the story then diverges. The hero finds no mysterious castle of a Fisher King. Instead, he travels to a Land of Maidens, alone defeats an entire army, and, near the end of the tale, discovers that the ring he has been wearing ever since an incident in a lady's tent when he first approached Arthur's court is a magic ring that has made him incapable of being killed.