Ailie is a character in the Genesis of Shannara trilogy. She was a tatterdemalion, a Faerie creature manifested from the memories of dead children. As a messenger of the Word, Ailie told Angel Perez, a Knight of the Word, that the Elves needed Angel's assistance.
Ailie first appeared to Angel Perez as the Knight was watching over thousands of children she had saved from the Anaheim compound before it fell to the demons. She convinced Angel that the Word required her to leave the children in the hands of others and to go north to the Cintra. There Angel would find the Elves and she could warn them of oncoming danger.
Ailie's Faerie nature allowed her to detect the demon Delloreen, who was pursuing Angel, when it drew close. Thanks to Ailie's warnings, Angel managed to evade Delloreen and get the both of them safely to the Elven capital of Arborlon.
When Angel and Ailie presented themselves to King Arissen Belloruus and the Elven High Council, they urged the Elves to flee the Cintra in order to save themselves from the coming demon onslaught. When the King dismissed their warnings, Ailie revealed to the High Council's surprise that the King has already been warned by Kirisin Belloruus and had chosen to do nothing at that time as well. Later, Ailie revealed to Angel and the Elves Erisha Belloruus, Simralin Belloruus, and Kirisin that a demon had been present in the King's council chambers, indicating that the Elves had already been compromised.
Ailie accompanied Angel and the Elves to Ashenell, the Elven burial grounds, to find the Elfstones. Ailie stood watch at the entrance to Ashenell because of her ability to sense the presence of demons. Sure enough, Ailie was able to sense Delloreen when the demon drew close to her, but she momentarily forgot about the other demon in Arborlon, who took Ailie by surprise while she was distracted and killed her. That demon turned out to be one masquerading as Culph, the King's historian.
Later, Simralin was only able to find the remnants of Ailie's gown. Being a Faerie creature, Ailie's body had melted back into the natural elements from which it had been made almost immediately after her death.
Ailie had the appearance of a small girl, maybe about ten years old. She had chalk-white skin, black eyes, and pale blue hair. While she did have a physical form, it was very insubstantial, and she seemed to be made mostly of light. She wore a light, thin white dress that seemed to be an extension of her body.