She appears to be a silver-skinned 20-year-old woman. Her hair is deep auburn, and her eyes are viridian. She's tall and waifish, yet carries herself elegantly in her green and grey dresses. She wears a dark green scarf that holds 1 breath from each of the wind and sky gods; granting her true sovereignty over the atmosphere.
She is graceful, but has little patience. When angered she is not afraid to pull no stops with her attacks. Wrathful, she also cusses enough to make a sailor blush. A bit prideful and haughty, she hates whatever enters her domain on wicked wings, magic, and other forms of flight. Her raw imperiousness is the glue that keeps her and her siblings from falling out with one another.
Sylph controls the air itself, shifting the winds, as well as the lesser birds who fly within it. When angry, she's been known to turn entire sections of air into doldrums, or even stopping all motion in the air, causing anything flying within to drop like a stone. She gets angry more and more often as time has been passing.
Great Mother Iisla - Queen of Harpies. She has six daughters, each the head of a different Clamor of harpies.
- Her eldest, Mother Zinia, is nest mother of the Pale Talon harpies.
- Her twin sons, Aetus and Esu, as males among a matralinial race they do not hold their own nests.
King Baron - King of the Griffons.
Sojobo - King Tengu.
Osu, Suraisu, and Iyashi - The Kamaitachi; sickle weasels.
The Peryton - Her steed. Last remaining of his kind after their flight from the destruction of Atlantis.
Gnome - Her brother, Spirit of Earth. She interacts with him the least, as he tends to keep more to himself. She sees him as stalwart and confident, and she trusts him the most out of her siblings to make mature decisions.
Salamander - Her other brother, Spirit of Fire. She sees him as reasonable, but believes he takes things too easily in stride. She worried for his safety while on Mars, and was heartbroken watching his tribes shrink, hide, or disappear entirely in his absence.
Undine - Her sister, Spirit of Water. The two of them are extremely close, however, with the last few centuries of Undine's laziness in Salamander's absence, she's been disappointed in Undine's lack of initiative in keeping order in the waters.
Father Garu - A good friend of hers. She occasionally stops to visit and talk with him on both good and bad days. When he gave his breath for the Scarf of Gods' Breaths, he gave it with a laugh.
Captain Johnathon Overland Strider - Sylph is a conditional ally with the UNSC fleet coming in and out of the atmosphere. She has an transmitter given to her by Strider, that sends a signal if he requests her help. Of course, she still chooses her own battles.
- Sylph is based on the spirit of the same name, named as the elemental spirit of air by the physician, occultist, and alchemist Paracelcus.