Ygraine Pendragon

Ygraine Pendragon (née de Bois) was the queen of Camelot through her marriage to the king, Uther Pendragon.

Biography
She and Uther were friends with the sorceress Nimueh. Ygraine was unable to bear children. Because he wanted a son, Uther asked Nimueh to use magic to allow Ygraine to give him a son. Nimueh agreed, and Arthur Pendragon was conceived and born. However, unknown to Nimueh at the time, the law of magic states that to create a life another must be destroyed. The result of this was Ygraine died in childbirth. Uther blamed Nimueh and all magic for her death and set about attacking all kinds of magic there afterwards, resulting in The Great Purge. (Excalibur)

It is unknown if Ygraine knew about Uther's affair with Vivienne, Gorlois's wife and possibly her own sister, which resulted in Morgana's birth. It, however, likely that she knew as Vivienne was her sister and Vivienne probably confided in her sister. (The Crystal Cave)

After Death
After her death, her brother, Tristan de Bois, blamed Uther and challenged him to a battle. Uther prevailed and killed him. 20 years later, Nimueh ressurected Tristan as a Wraith and sent him to fight Uther again. Uther used Excalibur to kill him. (Excalibur)

Apparitions
Morgause made her appear when Arthur wished for her to, and Ygraine told Arthur about his past, although the fact that this apparation claimed that Uther went to Nimueh with full awareness that Ygraine's life would be sacrificed for Arthur to live makes the nature of the apparation suspect at best, it is likely true. Arthur returned to Camelot and nearly slaughtered his father, but Merlin told him that Morgause was lying. Arthur currently believes that Uther was not to blame for Ygraine's death, even though he actually is. (The Sins of the Father)

When Morgana used a Mandrake Root to make Uther go mad, he hallucinated Ygraine calling to him for help, and then with children he had drowned in the Great Purge, traumatising him. (The Tears of Uther Pendragon)

Personality
Through hints in the series, it can be assumed that Ygraine was a much loved Queen when she was alive. She was probably more friendly and tolerant with the sorcerers than her husband was, because of the statement that Morgause says that Ygraine was a woman with much honour; Morgause also claims that she knew her very well, making the possibility that Ygraine had many friends who were sorcerers or, given her role in the legend, was Morgause's mother. When Arthur finally met her, she told him that she was very proud of him and that she would willingly give her life for him again.

Interestingly, when Morgause summoned her spirit to speak with Arthur, Ygraine claimed that Uther knowingly sacrificed her to get a son. Whether Ygraine honestly believes this or not is unknown since Morgause was using the knowledge of Arthur's birth in a plot to get him to kill Uther.

Appearances
Series 1:

The Mark of Nimueh (mentioned only)

The Poisoned Chalice (mentioned only)

Excalibur (mentioned only) [first identified as Ygraine Pendragon (DeBois)]

Series 2:

The Sins of the Father (first appearance) (appears as a ghost or spirit)

Series 3:

The Tears of Uther Pendragon: Part One (appears as a ghost of spirit)

The Crystal Cave (mentioned only)

Series 4

Historicity
Ygraine is classically portrayed as the wife of Gorlois prior to her marriage to Uther. With Gorlois, she has three daughters: Elaine, Anna-Morgause, and Morgan le Fey. Through Anna-Morgause, the Igraine of legend is the grandmother of Gawain, Gaheris, Gareth, Agravain, and Mordred, and, through Gawain, the great-grandmother of Florence, Lovell, and Gingalain.