The Sun, also called Sol, is the star at the center of the solar system While many spirits of light and fire claim to have originated there, no human has ever managed to approach it due to the tremendous heat and gravitational pressure.
The Order of Hermes sometimes still refers to the Sun as the "Shard Realm of Infinity," though there is considerable debate about what "infinity" means in this context. It also appears to have no corresponding Shade Realm, unless of course the Shade Realm of Infinity is the entire Tellurian.
The Celestine of the Sun is Helios, patron of the Corax and the Mokole.