Primus

The closest planet to Eua, Primus orbits approximately 23 million miles (0.25 AU) from the star. With an orbital period of only 44 days, the planet passes through the influence of each of the four elements in 11 days each. As a result (and as a result of the extreme elemental energies that close to Eua), the seasons are incredibly violent. Approximately the size of Mercury (~ 0.05 Quartus-masses and about 11% of the radius of Quartus), it has a mean density of about 8.0 kg/m^3. All sorts of materials unique to that conflux of elemental energies are found there. Beings from the various elemental planes and the astral visit Primus in search of particularly rare and powerful materials.