There are very few creatures who can innately use magic; for everyone else, there are valui. Valui are stones that can hold different types of elemental magic; they are taken from a mine outside the city. Both the mine and the distribution of valui are controlled by the temple, and in theory, anyone in the city can receive a valui stone. The element that the valui is imbued with affects where it is worn, due to chakra— see 'news chakra' for more information on valui placement.
The valui themselves are not merely rocks, but, it is believed, a divine blessing from the goddess Akasha. As such they are treated very carefully, and the cutting, polishing, and refining of them is a task given only to the most trusted and skilled priests— as monks in another place might take pride in the personal touches they put into illuminated manuscripts, so do the priests in charge of shaping valui and creating housings for them take pride in their work.
The temple does not give just any valui to whoever wants one; those requesting one will be taken to a room where the refined valui are held, and within, the priest performs a ritual. Afterwards, it is said, one of the valui chooses its wielder— although how this occurs is not quite certain, and the experience is considered a private one. Some believe that certain personality traits are associated with certain elements, and that this is how the valui attach themselves; others believe that the stones can feel a personal affinity with their users, and choose that way.
Either way, once the animal has received his or her valui, training begins. Although in theory any magic user of the same element and higher rank can train apprentices, there are adepts affiliated with the temple who have formed a kind of 'school'. These creatures take on students— one on one often, and certainly no more than three at a given time— to teach them how to use their valui in a more 'official' way. If the student wishes to learn how to perform a specific job, such as metalworking, someone within that field will likely take over after basic teaching is completed.
While the valui themselves are related to specific elements, and these are not innate, all animals have, so to speak, the 'gene' for a certain power. It takes magic use— valui or innate— to turn that 'gene' on, and typically, therefore, powers manifest themselves as the student's mastery of his or her valui begins to grow. The exception to this is the ability to fly: these creatures are born with their wings, but those wings remain undersized and stunted until magic use begins; then, the skeleton begins to shift and the wings begin to grow.