feino

The base root has no page here, so take it from the top. Feo is the creature - a fairy, a fae, of no particular sex. Add -in-, the suffix that makes the female of whatever the root is, and feino is a female fairy. It is the same derivation as reĝo giving reĝino a queen, viro giving virino a woman, bovo giving bovino a cow.

And then usage does something odd, so notice it. In practice feino has swallowed the whole word. The fairy of European folklore is almost always imagined female, so feino is what writers reach for when they mean a fairy at all, and feo survives mostly in dictionaries and in the rare sentence that specifically needs a male one. This is exactly what happened to vidvino - a widow - where the derived form is common and the base vidvo is not. Esperanto's affix system is regular; which of the regular forms people actually say is a separate question, decided by the world rather than by the grammar.

Fairy-tale furniture. The good fairy of fabelo has flugiloj (wings) and magia bastono (a magic wand - bastono is a stick, and the magic comes from the adjective). Feina means fairy-like, and the fairy godmother is a feina baptopatrino. If you want the tale rather than its cast, that is fabelo; feo and feino are who live inside it.