Neverwinter Nights Aribeth
Aribeth de Tylmarande
Lady Aribeth de Tylmarande was a half-elf paladin of Tyr, the Blind God of Justice.
She is said to have been born in Thundertree, a town in the Neverwinter Woods, of uncertain parentage; some say a union between half-elves, others a moon elf and a human. The village's population was wiped out in an orc raid leaving her the sole survivor of the massacre. Vowing vengeance, she hunted down the perpetrators and slew them all. Unsatisfied, she continued to hunt and kill orcs in an obsessive quest until she was trapped in a sudden blizzard and rescued by a one-armed man she believed to be an avatar of the god Tyr, who took her to a monastery of Ilmater. Recovering her health there, she learned to be a paladin, gaining such fame that when she moved to Neverwinter, she was named to the elite bodyguard of Lord Nasher Alagondar, being the first woman and first non-human to be so honored. There she met and became engaged to Fenthick Moss, a cleric of Tyr in the Hall of Justice.
Lady Aribeth was chosen by Nasher Alagondar to be in charge of the investigations surrounding the Wailing Death. She began training adventurers at an academy to combat the forces behind the plague, and after the Waterdhavian creatures needed for a magical cure became scattered throughout the city, the hero, who was an exceptional student at the academy, was placed by Aribeth in charge of tracking them down.
After her lover, Fenthick Moss, was found guilty by association and was hanged for trusting Desther Indelayne, a false Helmite and agent of Maugrim Korothir, Morag appeared to Aribeth in her dreams and tempted her to join Maugrim's cult with promises of revenge against the city that unjustly murdered Fenthick. Aribeth initially continued to lead Neverwinter's effort to find the cult in and around Port Llast, but eventually disappeared. When agents reached Luskan's Host Tower of the Arcane, they learned that Aribeth had become a blackguard in the service of Morag and had agreed to lead Maugrim's Luskite army in their impending assault on Neverwinter. At the climax of this assault, the hero confronted Aribeth and defeated her in combat. The hero could then either persuade Aribeth to surrender and return to Lord Nasher to face judgment or be forced to fight her to the death.
Hordes of the Underdark
Aribeth died not long after the forces of Morag were repelled. Upon encountering her spirit in Cania, Drogan's Pupil found her distraught with her betrayal of Neverwinter due to her realization that she never truly loved Fenthick; her betrayal therefore was not motivated by her love of Fenthick as she had thought and was consequently much less justified. The hero could either persuade her to return to the service of Tyr, or accept the evil path that she had chosen; either way, she could join the hero in his/her quest. Aribeth herself said that she died violently, though her memories were somewhat hazy. Presumably, the hero of Neverwinter attempted to defend Aribeth while she was tried for her crimes. The hero would have been heavily outvoted, since the majority of Neverwinter called for Aribeth's execution. Lord Nasher complied with the city's request and as a result, the hero of Neverwinter's friendship with Lord Nasher ended, and he/she (the hero is revealed to have been the sex of your character) left Neverwinter, never to be heard from again. Because of the hero's falling out of favor with Lord Nasher, Nasher had revisionists play down his role in saving Faerûn from destruction.
If Aribeth was at the protagonist's side in the confrontation with Mephistopheles, the archdevil would use his considerable charisma to play on her uncertainties and turn her to his side unless the player character could be even more persuasive.