According to
Historia Regum Britanniae, Gorlois was vassal of
Ambrosius Aurelianus, whose arrival at the Battle of
Kaerconan ensured the defeat of
Hengist. In
Wace's
Roman de Brut, when Hengist's son Octa and his cousin Ossa rebel, Gorlois helps Uther defeat them at
York. In the
Brut Tysilio, a Welsh version of Geoffrey's work, Gorlois is the father of
Cador, Duke of
Cornwall, presumably by Igraine. After he succeeds his brother, Ambrosius, Uther holds a feast for his nobles, and seeing Igraine, lusts after her. Sensing
Uther Pendragon's interest, Igraine asks her husband to take her back home to Cornwall. He placed her at the more defensible
Tintagel Castle, while he prepared to defend his territory from Dimilioc. Incensed at their departing without leave, Uther lays siege to Gorlois' castles to little effect. He consults his friend Ulfin who tells him that the lady can hardly look favorably on someone who makes war on her husband, and suggests the king seek advice from
Merlin in gaining access to Tintagel. Merlin devises an enchantment that
disguises Uther in the form of Gorlois. In this form he approaches Igraine and they sleep together, conceiving
Arthur. Unbeknownst to either of them, the real Gorlois has been killed that very night in battle against Uther's troops. This passage is a parallel of later stories of Gorlois and Igraine. Scholars
Rachel Bromwich and D. Simon Evans note the similarity between the
Gor- element in Gormant and Gorlois' names, which could reflect a known practice in some
late antiquity and
early medieval European dynasties to share a name
prefix. There is a possibility that Rica could be equated with
Ricatus (or Recgisi), a name found on an 11th century Cornish cross. The
Peniarth triads give the same title—Arthur's chief elder at
Celliwig, Cornwall—to
Caradoc, which could also equate him with Rica. The 13th century
Prose Merlin calls Ygerne's husband Hoel, Duke of Tintagell, with
Ydiers as king of Cornwall. Hoel and Ygerne have five daughters together, who marry
King Lot,
King Ventres,
King Urien, and King Briadas.
Richard Carew's
Survey of Cornwall (1602) places Gorlois as husband of Igerna and duke of Cornwall in 500 AD, who is succeeded by Earl Cador by 526 AD. The
Book of Baglan (1600–1607) calls him Gurleis, Goulisor, or Gwrleis, duke or prince of Cornwall, and husband of Eigyr; he is the father of Cador, and son of Sortogus, a direct male-line descendant of
Maxentius,
Dyfnwal Moelmud,
Camber and
Brutus of Troy.
William Worcester travelled to Cornwall in 1478, and recorded in his
Itineraries that "Tador Duke of Cornwall, husband of the mother of Arthur was slain" at
Castle an Dinas. This is generally interpreted as a conflation of Gorlois with Cador, and as an alternative place of Gorlois' death, differing from the
Historia Regum Britanniaes account that he died at Dimilioc. ==Possible historicity==