In her human form, Sibyl looks young and smallish but athletic. She has chin-length brown hair, and she usually wears either silver armor or a white one-piece swimsuit (She's a little shy about public nudity in her human form.) She always wears a single silver earring.
In her sphinx form, she is almost twice as large and has soft, tan fur and brownish wings, like those of a golden eagle. Her build is like that of a feline, and her broad paws have retractable claws. Her head remains furless and mostly unchanged, but her hair becomes longer. Much more well-endowed in this form, she has a single pair of ample breasts and more mature-looking curves. She can walk on two paws or four.
Sibyl is attracted to both males and females, with a current slight preferece for females (She became a werephynx as the result of a true female sphynx who had her way with her.) Her sex drive is greatly increased while in her sphynx form. She can be slow to make friends, especially when human, but she often approaches furs she considers non-threatening. Having been trained in chivalry, she tries her best to be polite with everyone, even those who make unwelcome advances. This also gives her a slight soft spot for courtly romance.