The Old Realm was the Creation-spanning state headed by the Solar Exalted during the so-called High First Age, in accordance with the Mandate of Heaven. While individual Exalts ruled specific territories as kings and queens, they were brought together in the Solar Deliberative to make collective decisions about the future of Creation.
The Old Realm was a golden age of sorcery, engineering, art and exploration, but its greatness rested on the power of the increasingly unstable Lawgivers. The Usurpation replaced the Old Realm with the Dragon-Blooded Shogunate, ushering in the Low First Age.