This pony is inspired by the magic of the will o' the wisps.
Willow Whisp is a spirit pony - hence the ghostly cutie mark. In being a spirit pony she can change her shape at will, even she doesn't know her true form. Her mane is often transparent, sometimes making her almost invisible to others. Also, Willow is very quiet and shy. Did I mention she's an alicorn?
Click the picture above for full size. What do you guys think? Any drawing critiques? Please don't take my design, she's my per-pony-fication and my original work. Thanks!