Lugh the High King was born to Cian of the Tuatha Dé Danann, and Ethniu, daughter of Balor of the Fomorians. Balor was the king of the Fomorains who possessed a powerful predecesor to the Mystic Eyes of Death Perception - who could actualise death of an object by merely looking at it.
Balor heared a prophecy that he would be killed by his grandson. To avoid his fate, he locked his only daughter, Ethniu, in a tower on Tory Island to keep her from becoming pregnant. One day, Balor stole a magical cow. A man called Cian, who was guarding the cow for Goibniu, sets out to get it back. With the help of the druidess Biróg and the sea god Manannán, Cian enters the tower and finds Ethniu. After a night together she became pregnant and gives birth to three sons. Balor attempted to drown the boys in the sea, but one is saved and is raised as a foster-son by Manannán. This child was Lugh.
As a young man Lugh travels to join the court of king Nuada of the Tuatha Dé Danann. He offers his services first as a Wright and then as a smith, a champion, a swordsman, a harpist, a hero, a poet and historian, a sorcerer, and a craftsman, but is rejected as the Tuatha Dé Danann already have someone with each skill. But when Lugh asks if they have anyone with all those skills simultaneously, the doorkeeper has to admit defeat, and Lugh joined the court.
Lugh eventually became king of the Tuatha Dé Danann and lead them in the second Battle of Mag Tuired against the Fomorians, who are led by Balor. Balor kills Nuada with his eye. Lugh kills Balor by casting a sling, through his eye. Balor's ruptured eye destroys the Fomorian army and was the destroyed by Lugh.
Later on, when the sons of Tuireann, Brian, Iuchar and Iucharba, kill his father, Cian Lugh set them a series of "Labours" to repent - with the purpose of killing them in the proces. They achieve them all, but are fatally wounded in completing the last one. Despite Tuireann's pleas, Lugh denies them the use of one of the items they have retrieved, a magic pigskin which heals all wounds. They die of their wounds, and Tuireann dies of grief over their bodies. Lugh died of old age. He became known as the greatest king in the history of Ireland and after he died, he ascended to godhood and became the sun god known as the 'Father of Light'.
Although once a mortal hero, he became a king of gods upon his death and a fully fledge divine spirit. It is impossible to summon Lugh in full as a servant. Due to these complications with his summoning, Lugh has become a pseudo-servant with his soul manifesting inside a Magus who currently wields his sword. The magus is Bazett Fraga McRemitz.
As a Pseudo-Servant, the combined existence that is Saber is neither Lugh or Bazett - combining strengths and weaknesses, showing a power that is not that of the original servant.
Lugh has decided to take a back seat so to speak and allow Bazett to command their shared body with her usual temperament - the constant company helping her with her loneliness issues although it is a nature she finds bothersome. During times of intense duress or excitement, Lugh's repressed personality comes forth acting haughty and arrogant.
Due to Lugh's fatherly feelings towards his son Cu Chulainn and Bazett's own more romantic feelings, she would stay far away from him in every respect as Bazett and Lugh do not want to discuss the subject with each other.