Spoiled child and perfectionist law-breaker commits breaking and entering, home invasion, invasion of privacy, grand-theft porridge...? Also flees the scene of her crimes.

Seraide was a handmaiden, high priestess, damsel or retainer in the service of the Lady of the Lake. Her only known mission was to rescue Bors and Lionel, taken captive as children after their parents, a king and queen were killed. She delivered them to the Lady of the Lake to be reared along with their cousin, Lancelot.

Gwendoloena (Gwendoleu) was Merlin's wife, though apparently only one tale of her exists. It's tied to the stories where his visions were driving him mad, until his sister took them upon herself. His sister, Ganieda, also took care of his wife while he was lost wandering the woods. When he was returned, he released her from their marriage, but said that she could only remarry if her new husband never saw Merlin.
 
When she was prepared to remarry, Merlin showed up on a stag with a retinue of deer. She laughed at the sight of it and prompted her fiance to come see. Merlin then threw an antler into the man's heart, killing him.
 
Gwendoloena wasn't heard from again, but it's interesting to note how hard Merlin later falls for Nimue, a huntress/forest maiden.

Rossignol is the name given to one of the handmaidens of the Lady of the Lake. When she failed in a mission, Rossignol ran away and joined a convent rather than face her failure.

Dame Ragnell, the "Loathly Lady," was a disheveled old hag who once saved Arthur's life. She later recalled the favor by asking for a knight to marry. Despite her being apparently fairly frightening, Sir Gawain nobly offered to marry her for his king.
 
She demanded a very public wedding when she married the handsome young knight. She also dressed extravagantly and ate great quantities. Ragnell was considered wicked for doing all this, as it was believed to bring shame to Gawain. However, he had never been known to be discourteous to a lady (or really anyone, I suppose), and took it all in stride. When she asked to consummate their marriage, he obliged.
 
After this, she appeared to him as a beautiful young woman. She revealed that she had been cursed, and could either be young by day and old by night, which she would prefer, or old by day and young by night, which would be preferable for him for reasons that should be fairly obvious. The choice had to be his, she said. Being the bang up guy he was, he chose for her to be young by day and old by night, her preference. By giving her her own choice, the curse was broken and she would now be in her true, youthful form full time.
 
Ragnell was self-possessed, unabashed, and quite good with riddles. Kings and knights were at the mercy of her wit and disregard for convention. It's said she didn't have a long life, but Gawain mourned her for the rest of his. She gave birth to a son, Gingalain, who would become a romantic hero himself.

Unbeknownst to Morgana's husband, Uriens, and her brother, Arthur, there was another man she loved, Sir Accolon of Gaul. At a time when Arthur trusted his enchanted scabbard, which would prevent it's wearer from harm, she forged a duplicate and returned that to him. She gave the real one to her lover, Accolon.
 
Later on a hunting trip, Arthur and Accolon and kidnapped and forced to battle each other in disguise. Arthur was losing badly when he realized his opponent was under the protection of his own scabbard's magic. Lucky for Arthur, a fairy or Lady of the Lake (for the most part they seem to indicate either Nimue or Nyneve) became aware of Morgana's deception and used magic to switch things back.
 
Arthur dealt a crushing blow to Accolon's head, causing a fatal concussion. When Accolon's helmet was removed and his identity was revealed, Morgana's treasonous actions also became clear. Accolon's body was sent to Morgana's castle, causing her great sadness and escalating the enmity between her and her brother.
 
I'm a little unclear on how far back the character goes in these cycles, but he seems to have some sort of Celtic dog cult association attached to him.

Annowre was a sorceress who tried to seduce Arthur from her tower in the Forest Perilous. She used spells to capture the King to work on said seduction. Nimue, being a creature of the forest herself, sensed this and, enlisting the help of Sir Tristram, broke the spell and rescued Arthur. Arthur beheaded Annowre for her troubles and Nimue kept her head tied by the hair to her saddlebow.

Lunette (French for "little moon), was the cousin of Vivienne (Lady of the Lake) and had mystical traits of her own. She features in Yvaine's story as the one who gave him a ring that could render the wearer invisible and she set him up with Laudine.
 
She was known for being clever, prudent, kind and distinctly brunette. She was a lover of Gawain. This last fact suggests a possible connection to older myths, given Gawain's association with the sun and Lunette's with the moon.

Sir Bors (French: Bohort) was the cousin of Lancelot, and eventually he and his brother Lionel were raised by the Lady of the Lake along with him. Bors was known for a distinctive facial scar. A scarred knight, but generally one whose death stories do not detail, his survival of his comrades and loved ones is perhaps a defining trait as well.
 
Along with Percival and Galahad, Bors was one of the Grail Knights. He lived a celibate life except for one night with Claire, daugher of the King Bradegoris. By some accounts she seduced him with help from a magic ring. She bore him a son, later a knight himself, known as Elyan the White (Helyan le Blanc).
 
Aside from this, there are also some tales of women who by turns appealed to his compassion in attempts to get him into bed. He refused and eventually they were revealed to be succubi.
 
When given the choice between saving his brother Lionel, and a maiden who was also in danger, he saved the maiden. Lionel survived and later tried to kill Bors, but spontaneous combustion or divine intervention in the form of a column of fire saved him when he refused to defend himself from the his brother's wrath.
 
When the Grail Knights found the grail and returned it to Sarras, Galahad suffers an ecstatic death, perhaps bordering on some sort of knightly apotheosis, and ascended to the heavens along with the cup. Percival shortly went tumbling after. It was Bors who survived and returned to Arthur's court.
 
When Guinevere stood accused of crimes and Lancelot was absent, Bors agreed to defend her. Lancelot did show up, and Bors sided with Lancelot against Arthur when the time came.
 
Bors returned along with his kinsmen to defend Camelot from Mordred. Lionel was killed in battle against Melhan, a son of Mordred, and Bors avenged him.
 
He eventually returned to Joyous Guard, learned of Lancelot's death and ended his days in a monastery.