"Tall and wiry, this githyanki's chiseled muscles and graceful motions are the trappings of a soldier built for endless war. The skin of her face is pulled so tight across her bony head that her cheeks and forehead twitch with her pulse. She does not make eye contact with you, but rather focuses with unblinking intensity on your chest. As if responding to her stare, you find your stomach tying itself in knots and your heart beating irregularly."
Zeeaire is a githyanki sword stalker, one of the highest ranking ones in service of the Lich Queen Vlaakith. As the King of Shadows was beginning to re-emerge in Faerun at the Mere of Dead Men, she sent a githyankiu raiding party to West Harbor with the intention of retrieving all the shards of the silver sword that shattered in the battle with the King, and branded the PC as the Kalach-Cha ("shard bearer"). They set up base in old Illefarn ruins near Duskwood Forest.
It is unlikely however that she told her minions the full story of the shards, as it was no ordinary silver sword, but the Silver Sword of Gith. The sword had gone missing with Gith in the Nine Hells of Baator long ago, and was only recovered by Ammon Jerro and Mephasm down in Stygia. She stressed the importance of the recovery of the shards, cryptically ordering them to "forget the betrayer, forget our vengeance" and to find all the shards.
Both the PC and the Githyanki soon learned of Ammon Jerro's last surviving relative: his granddaughter Shandra Jerro. Though the githyanki were driven off at her farm, they eventually captured her at the Sunken Flagon and took her back to their base near Duskwood. With Bishop, they traced them through Ember and on to the hilltop ruins in a cavern. They were not the only ones seeking out the githyanki; Ammon Jerro arrived with his demon army intent on taking the shards the sword stalkers had found.
After battling through succubi, charmed githyanki, and Jerro's fiends, the PC encountered Zeeaire, within an astral portal. She condemned him/her as a criminal, over the "theft" of the shattered sword, and intended to execute the PC for crimes. She also intended to torture all possible information Shandra had on Jerro's Haven, and eventually finish her off as well as Ammon's "crime" had passed to her since he died (unaware that Ammon was in fact alive and back in Faerun).
Zeeaire forced the three shards the Kalach-Cha had, and discovered another was lodged in his/her chest. Zeeaire ordered her minions to attack, but the PC was able to destroy the astral portal, forcing Zeeaire fully into the Realms. No longer in the timeless Astral Plane, Zeeaire was very mortal and vulnerable to aging. As the player defeated her, she told of the King of Shadows impending return from the Plane of Shadows and their "doom," and spitefully deemed it as a fitting punishment to the Kalach-Cha and his/her world before withering away and dying.
The fact Zeeaire didn't arrive to search out the shards until the last minute is somewhat suspicious, as the sword was "stolen" and shattered decades earlier. The fact she knew more about the shards' nature than she told her subordinates suggest an ulterior motive beyond merely retrieving a stolen silver sword, or perhaps even beyond preparing to fend off the King of Shadows.
Under certain persuasion checks, it becomes clear she is hiding something, and her guards will wonder if they should report back to Vlaakith on their activities, which Zeeaire dismisses as manipulation. It's possible she was intending to restore the sword to usurp the Lich Queen, and sent the sword stalkers for that end.