What are Nifflers?
Nifflers are British beasts. Fluffy, black and long-snouted, this burrowing creature has a predilection for anything glittery.

Nifflers are often kept by goblins to burrow deep into the earth for treasure. Though the Niffler is gentle and even affectionate, it can be destructive to belongings and should never be kept in a house. Nifflers live in lairs up to twenty feet below the surface and produce six to eight young in a litter.

Nifflers have a pouch on their bellies which holds far more than at first seems possible, like the effects of a Undetectable Extension Charm on a container.