The True Horizon, also called Subspace by the Technocracy and Etherspace by the Sons of Ether, is a vast expanse of the Umbra located between the Near Umbra and Far Umbra. To Sleepers, it manifests as the space between the Sun and the asteroid belt. Within it are several Horizon Realms, as well as four Shard Realms, which manifest as the Sun and inner planets.
- The Sun
- The Moon
- Its spiritual reflection is the Celestine Luna
- Some believe that Arcadia is the Shade Realm of Luna. Others posit that the Earth and Moon together form the Shade Realm of Prime, which is the reality of humanity. Still others claim that the Moon has no Shade Realm at all. There is little agreement among mages, much less between Traditions
- Victoria Station and Darkside Moon Base are located here
There have been numerous debates and arguments over whether Earth is a Shard Realm itself, or instead the center of a deeper reality.
Known Horizon Realms
- Horizon, the metonym stronghold of the Nine Traditions
- Mus, which orbits Mercury, invisible to Sleepers
- Balador, the treasure of the Cult of Ecstasy
- The Gernsback Continuum, the Sons of Ether's Realm of wild science
- Midrealm, which lies at spiritual center of the Middle Umbra, and perhaps the center of everything
- Autochthonia, which circles the Sun in direct opposition to Earth and is the off-world home of Iteration X. Some claim that it is more than a Horizon Realm, perhaps even the embodiment of the Shenti of Stasis itself
- - "Chapter Five: Celestial Bodies"