The Leanansidhe

The Leanansidhe, or Lea, is a faerie of the Winter Court and Harry Dresden's faerie godmother. She first appears in Grave Peril.

Description
The Leanansidhe has curly copper-scarlet hair, and amber eyes.

She is considered one of the higher Sidhe within the Winter Court and held a position of power up until her imprisonment by Mab. She has made no objection to Harry Dresden calling her "Lea", although she has objected to being called a faerie rather than one of the Sidhe.

Despite being 'treated', it is still readily apparent that, by mortal standards, she is less than mentally sound, evidenced by her childlike behavior and excitement at times of extreme violence such as Dresden's victory in the duel near the conclusion of Changes.

Biography
Lea has made a deal with Harry Dresden when he fled from his adopted father, who had tried to coerce him into performing black magic at the age of 16. Lea agreed to give Harry the strength necessary to defeat DuMorne, in exchange for his life, fortune, and power. In actuality Harry already had the strength he needed, so all Lea really gave him was confidence. Of course confidence is a very great gift in itself, so what Lea gave him probably saved his life and mind. Her torture sessions essentially handed Harry Dumbo’s magic feather: they made him think he was better, stronger, and faster without actually altering a damned thing, otherwise. And it worked. He overcame DuMorne. This deal was reinforced by another similar deal made by Harry during the course of Grave Peril. The debt from these deals was sold to Queen Mab before the events of Summer Knight.

Grave Peril
In Grave Peril, Lea has spent many years attempting to get Harry Dresden to honor his bargain and become hers to which she has expressed the desire to turn him into a hellhound as evident in which Lea chases Harry Dresden and Michael Carpenter in the Nevernever.

Summer Knight
The Leanansidhe indirectly assists Harry Dresden by posing as an elderly woman calling the cops during a fight with Grum. She later takes him to an ethereal Chicago-over-Chicago and a great Stone Table on his task for Mab.

Proven Guilty
In Proven Guilty, Lea is shown to be trapped in Arctis Tor, during which she exhibits signs of a personality more ruthless and devious than her dominant one.

Changes
In Changes, Lea lulled the vampire parts of Susan and Martin to sleep, possibly demonstrating a way to treat half vampirism. Lea claims that she was being treated for an ailment by Mab during her imprisonment. She told Harry that she would safeguard his treasures that he left in her garden. At Harry's request, Lea gave him his mother's jewel containing all her knowledge of Ways.

Lea was present at the Stone Table when Harry made his bargain with Mab to take up the Winter Knight's Mantle in exchange of strength, aid and time to save his daughter, Maggie. She reminded him of her warning to him years back to never let Mab bring him to the Stone Table. While there, she acts as interpreter for Mab since her voice would make his ears bleed. After the bargain is made, Mab assigns Lea with the task of aiding Harry on his quest—Mab said Lea may indulge herself.

Lea picks up Harry in a limo driven by Glenmael and outfits Harry and Susan Rodriguez for the quest and returns his stash which included Bob and the Swords. Lea goes on the quest with Harry to Chichén Itzá to save Maggie. Thoward the end of it, she impersonated one of the Lords of Outer Night to aid Harry in defeated the Red King. Lea arranged a Way back through Donar Vadderung that led directly to Saint Mary of the Angels where they started the quest.

Ghost Story
In Ghost Story, Lea was sent by Mab to continue Molly's training in her obligation to his Oath of Fealty—she's training her in combat skills. Lea talks with Harry's ghost while watching Molly fight the Fomor servitors. Harry makes her buy Molly's breakfast. Sometimes Lea takes turns with Molly and poses as the Ragged Lady. Harry recalls in vivid detail his battle with He Who Walks Behind. Lea bargains with Harry for the rest of the tale in exchange for three questions. Lea told Harry about Corpsetaker for his second question. She couldn't answer him directly about "who killed him" so she gave Harry's ghost three "true" answers despite "Eternal Silence"'s warnings.

Bombshells
In Bombshells, Lea trains Molly Carpenter in survival, rough living and combat, before assigning her the rescue of Thomas Raith in the Svartalf stronghold.

Cold Days
In Cold Days, Molly Carpenter states that Auntie Lea taught her the locations of ley nodes around Lake Michigan a few months prior. Harry Dresden gives the map to her to mark. It is mentioned that the ailment afflicting Lea was an Outsider entity called "Nemesis" with a mind controlling influence taking possession of who it inhabits. Mab can cure the Outsider taint given time and the willingness of the afflicted. As Maeve was not willing to change back to normal, Mab could not cure her like she did Lea.

Word of Butcher
Lea serves as Harry Dresden's godmother because of a deal she made with his mother, Margaret LeFay, before she died. Not much is known about the deal other than that she was in a rush, so she wasn't as detailed as she would have wanted it to have been.

Lea first appeared to Harry before he was adopted by Justin DuMorne, although he did not know who she was other than a lady who did nice things for him, until after his adoption.

In myth
In Celtic myth, the leanan sídhe ("fairy mistress") is a fae or type of fae known for taking human lovers and providing them with artistic inspiration, at the cost of madness and an early grave.