Raffia (ラフィア, Rafia) is the substance that supresses transplant rejection response caused by the immune system. Lux was built for the sole purpose of raffia-mining. Raffia is found in the center of Lux. Lux is controlled by the Class, and raffia is delivered to the Hill. Later it's revealed that it actually no longer serves a purpose and is simply being produced as a matter of procedure.