Lady Aribeth de Tylmarande is an elven paladin of Tyr, the Blind God of Justice, said to be among the foremost of Tyr's paladins in all the Sword Coast. She is renowned for her beauty, knighted for her faith, and beloved for her kindness. As one of Lord Nasher Alagondar's most trusted advisors, she is entrusted with finding a cure to the deadly Wailing Death.
Aribeth de Tylmarande is said to have been born in Thundertree, a town in the Neverwinter Woods of uncertain parentage; some say she came from a union between half-elves, others say between a moon elf and a human. The village 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. She gained such fame that when she moved to Neverwinter, she was named to the elite bodyguard of Lord Nasher, being the first woman and first non-human to be so honored. There she met and became engaged to Fenthick Moss, cleric of Tyr in that temple.
In the original campaign, Lady Aribeth is chosen by Lord Nasher to be in charge of the investigations surrounding the Wailing Death. She begins training adventurers, including the hero of the campaign, at the Neverwinter Academy to combat the forces who are behind the plague. After the Waterdhavian creatures become scattered throughout the city, the hero is placed by Aribeth in charge of tracking them down. The hero's quest ultimately leads to trusted friends of Fenthick Moss, Aribeth's lover, and Fenthick is found guilty by association and is hanged. Aribeth views this as a betrayal of Fenthick by the City of Neverwinter.
In the midst of her grief and anger at the city, Morag appears in Aribeth's dreams, offering a chance at revenge if Aribeth were to join Maugrim Korothir's cult. When Neverwinter's search for that cult locates its base of operations, Aribeth absconds from the service of Lord Nasher, becoming a fallen paladin (she would have been a blackguard, but that class was not included in the original game). She then leads an army in an assault on Neverwinter, during which she is confronted by the hero, who defeats her in combat. The hero may then either persuade Aribeth to surrender and return to Lord Nasher to face judgment or push the fight to the death. The persuasion option is somewhat difficult to pull off, unless the hero possesses the ring Aribeth gives to male PCs who listen to her full tale in chapter 2 (getting her to start the tale requires a modified intelligence of at least 9).
Hordes of the Underdark
In the Hordes of the Underdark campaign, Aribeth's spirit is encountered in Cania, distraught with her betrayal of Neverwinter. (She did not survive the aftermath of the original campaign, although the exact cause of her death is left vague to accommodate the possibility of her having surrendered.) The hero can either convince her to return to the service of Tyr, or accept the evil path that she has chosen. In either case, she becomes a multiclassed paladin / blackguard, but she will only progress in the class corresponding to her chosen path. In addition, she will be willing to join the hero as a henchman.
Aribeth is one of the romance options available to male heroes in the Hordes of the Underdark campaign. Completing the romance storyline with the paladin Aribeth allows for an easier persuade check to prevent her from being tempted away by Mephistopheles. In this scenario, the epilogue reveals that Aribeth and the hero became lovers, remaining together until the day he died (being a ghost, Aribeth had remained unchanged, while the hero grew old and gray). In his dying moments, the hero promises to meet her in the other life and so her spirit fades from the mortal realm to meet him and continue the rest of their existence together.