Feystone

Feystones are used by Nobles to store mana and also to make their travel mount called the highbeast.

Highbeast
By giving the feystone mana it can be morphed into the shape of an animal, that will move according to the user's will and fly through the air. The changes according to the user's imagination. Nobles generally change it into a mount eg Pegasus, Griffin or some other animal with wings. Auds family in Ehrenfest generally change their beast into a lion with wings. The Aud mount for Ehrenfest is a lion with 3 heads.
 * Rosemyne - when she was given a feystone and started to learn to expand the feystone she makes it into a balloon and as it grows bigger and bigger, she imagines it popping which it does. Ferdinand is quite annoyed as the stone is very expensive but to his surprise she changes what she has in hands to clay and goes round picking up the bits and puts them together which shocks him. In the end she makes a unique highbeast, a car (with seat belts and steering wheel) shaped red panda with a big tail, which Ferdinand says she make the tail smaller so as not to waste mana, which she doesn't.

Storage
Feystone can be used to store mana and can be re-absorbed back in to the user for future use. If you put too much mana in to a stone it can break down to gold dust. The feystones come in different qualities which means they can store different amounts of mana. The feystones which hold the large mana are very expensive.