Who is The Green Wind, the Leopard of Little Breezes from The Girl Who Circumnavigated Fairyland in a Ship of Her Own Making and what is their importance?

The Green Wind, one of several powerful winds barred from manifesting in Fairyland by the rules of the Marquess, kidnaps September from her home and brings her to Fairyland. He is accompanied by the mostly silent, but very powerful, Leopard of Little Breezes, one of a very few beings licensed by the Marquess to fly within Fairyland's borders. The Green Wind is playful and strong, loving and compassionate, a bit of a rule breaker, and ultimately a source of wisdom and support during a very dark time in September's journey.