The earliest known mention of a possibly historical Medraut is in the Welsh chronicle Annales Cambriae, wherein he and Arthur are ambiguously associated with the Battle of Camlann in a brief entry for the year 537.

As Modredus, Mordred was depicted as Arthur's traitorous nephew and a legitimate son of King Lot in the pseudo-historical work Historia Regum Britanniae, which then served as the basis for the subsequent evolution of the legend from the 12th century.

Later variants most often characterised Mordred as Arthur's villainous bastard son, born of an incestuous relationship with his half-sister, the queen of Lothian or Orkney named either Anna, Orcades, or Morgause.

The accounts presented in the Historia and most other versions include Mordred's death at Camlann, typically in a final duel, during which he manages to mortally wound his own slayer, Arthur.

In a popular telling, originating from the French chivalric romances of the 13th century and made prominent today through its inclusion in Le Morte d'Arthur, Mordred is a power-hungry son of Arthur from the incest with Morgause, prophesied by Merlin and destined to bring Britain to ruin.

The name Mordred, found as the Latinised Modredus in Geoffrey of Monmouth's Historia Regum Britanniae, comes from Old Welsh Medraut (comparable to Old Cornish Modred and Old Breton Modrot).

The more important of these, found in an appendix to the 9th-century chronicle Historia Brittonum (The History of the Britons), describes his marvelous grave beside the Herefordshire spring where he had been slain by his own father in some unchronicled tragedy.

An early 12th-century Italian high relief known as the Modena Archivolt seems to show a scene of abduction of Guinevere inspired by an original Welsh Arthurian tradition, perhaps as retold by Breton and other continental bards in their otherwise unrecorded oral stories.

[15] The unhistorical account presented by Geoffrey narrates Arthur leaving Modredus in charge of his throne as he crosses the English Channel to wage war on Lucius Tiberius of Rome.

[19] The 12th-century poems of the emerging chivalric romance genre such as those by Chrétien de Troyes, dealing with the adventures of various knights during Arthur's reign, would typically not mention Mordred at all.

This episode, sometimes dubbed the "May Day massacre",[note 1] leads to a war between Arthur and the furious King Lot, acting on his belief that he is the biological father of Mordred.

Lot dies in a battle at the hands of Arthur's vassal king Pellinore, beginning a long and deadly blood feud between the two royal families.

[21] In this branch of the legend, following his early life as a commoner, the young Mordred is later reunited with his mother, which happens long after Merlin's downfall caused by the Lady of the Lake.

Mordred displays stronger knightly values in the Vulgate Cycle (as does Gawain too in comparison to his later Post-Vulgate portrayal), where he is also shown as womanising and murderous, but to a significantly lesser degree.

Afterwards, a series of inconclusive engagements follows, until both sides agree to all meet each other at the one final battle, in which Mordred typically fights exceptionally well while commanding the loyalty of thousands of men willing to lay down their lives for him against Arthur.

In Henry of Huntingdon's retelling of Geoffrey's Historia, Mordred is beheaded at Camlann in a lone charge against him and his entire host by Arthur himself, who suffers many injuries in the process.

He also kills Sagramore in addition to six other Round Table knights loyal to Arthur in the Post-Vulgate depiction of the battle, which presents this as an incredible and unprecedented feat.

Later, as it had been commanded by the dying Arthur, the Archbishop of Canterbury constructs the Tower of the Dead tomb memorial, from which Bleoberis hangs Mordred's head as a warning against treason.

[31] In Ly Myreur des Histors (The Mirror of History) by writer Jean d'Outremeuse, Mordred survives the great battle and rules with the traitorous Guinevere until they are defeated and captured by Lancelot and King Carados in London.

In early literature derived from Geoffrey's Historia, Mordred was considered the legitimate son of Arthur's sister or half-sister queen named Anna or Gwyar and her husband Lot, the king of either Lothian or Orkney.

Today, however, he is best known as Arthur's own illegitimate son by his beautiful half-sister and Lot's wife, known as Morgause (Orcades / Morcades / Morgawse / Margawse), the Queen of Orkney.

Besides him, Mordred's other brothers or half-brothers often appearing in literature include Agravain and Gaheris in the tradition derived from the French romances, beginning with the prose versions of Robert de Boron's poems Merlin and Perceval.

In John Mair's Scottish Historia Maioris Britanniae, Arthurus, Modred and Valvanus (Gawain) were all said to be underage and thus unfit to rule, with Arthur described as a bastard, though Mordred is also not depicted heroically when he uses mercenaries to seize both the throne and Guanora (Guinevere).

[33] The 18th-century Welsh antiquarian Lewis Morris, based on statements made by Boece, suggested that Medrawd had a wife named Cwyllog, daughter of Caw.

[38] The perhaps 15th-century Spanish chivalric romance Florambel de Lucea tells of the surviving Arthur having been saved by his sister Morgaina (Morgan) in a later battle against the sons of Morderec (Mordred).

In modern adaptations, the character of Morgause is usually conflated with that of Morgan, typically cast as Mordred's villainous mother (or alternatively his lover or wife), often manipulative and sometimes abusive.

In Dante's Inferno, he is found in the lowest circle of Hell, set apart for traitors: "him who, at one blow, had chest and shadow / shattered by Arthur's hand" (Canto XXXII).