Jarvey - a creature that looks like an overgrown ferret, found in North America, Britain and Ireland. They live underground and they hunt voles, moles, rats and gnomes. Its most notable characteristic is the ability to talk. The jarvey doesn't talk in an intelligent fashion, however. It mostly spews out a constant string of short, frequently rude comments.

Jelly Legs Jinx (Spell) - which makes one's legs weak.

Jobberknoll - a small blue and speckled bird native to northern Europe and America, having magical feathers used in truth serums and memory potions. Unlike most birds, the jobberknoll is silent -- until the last moment of its life, that is, when it screams out every sound it's ever heard in its life, emitted in reverse like a tape played backwards.