Kay (Cai or Cei)

   Sir Kay was Arthur's earliest companion and foster-brother showing up in the Welsh tales such as Kilhwch and Olwen. In the early history, he was a bold fighter and slayer of monsters, such as the terrifying Anglesey cat (the Palug Cat). He was one of the noble knights and represented Arthur's conscience, often reminding him of the right and honorable course of action. According to the Welsh pedigrees, Kai was the son of Cynyr Cainvarvawc, the son of Gwron, the son of Cunedda Wledig. In the Triads, he is called one of the three diadem'd chiefs of battle, and is said to have been possessed of magical powers, by which he could transform himself into any shape he pleased. Of his real history, however, nothing is known. It is supposed that Caer Gai, in North Wales, bears his name; and it was the opinion of Iolo Morganwg, that his grave was at Cai Hir, at Aberavan, in Glamorganshire.
   Kai's horse, according to the Welsh authorities, was called Gwineu gwddwf hir, the long-necked bay.
   Later in the legends, his character was merged with Bricriu, the Irish troublemaker of the Red Branch, and his actions of conscience became bitter. His disagreeable side became more pronounced: taking offence at a quip by Arthur, bullying and spite towards the junior members of the court, and a series of bungled tasks undertaken in a boastful spirit. In the Grail stories and Peredur, he beats a young maiden and dwarf because of Perceval's arrival at Arthur's court and is the reason for Perceval's departure from the court. In the Perlesvaus, he kills Arthur's son, Llacheu and becomes Arthur's enemy. But in the end, Kay is at Arthur's side and proves that he can still conduct himself honorably.
   In most of the stories, he is Arthur's seneschal. There have been some arguments that this role and his name are a corruption of the Roman Latin 'cais', the equivalent of a tax collector or financial officer in the Roman provinces. His name may also be a shortening of the Latin 'Caius'.

Kay in Malory's le Morte