Who is Ell from The Girl Who Circumnavigated Fairyland in a Ship of Her Own Making and what is their importance?

Ell's mother was a wyvern, and his father was a library. Raised with his father, Ell studied and memorized all the books of the encyclopedia from A to L - that, in fact, is his name, A-to-L, which September shortens to Ell. When they meet, Ell has his wings bound in iron chains - like all but a very few of Fairyland's inhabitants, he has been prohibited from flying by the rules of the Marquess. Ell accompanies September on her journey, but is kidnapped by the Marquess, held prisoner in the Lonely Gaol, and has to be rescued by September. When offered the opportunity to have his chains unlocked, and therefore have the freedom to fly, Ell refuses, saying he can't justify having freedom when his siblings and so many other fairy folk are still imprisoned. In making this decision, Ell manifests two of the narrative's primary themes, the power of choice and the value of self-sacrifice.