The Hieroprince belonged to the Opaline Creed belief system. This religious group was situated on the Outer Rim planet of Crucival during the Galactic Empire's time. Reportedly, the Hieroprince fathered at least two sons, with Umu being the name of the second. By 4 BBY, the Creed had given at least seven members the name Umu, and they possessed a sacred writing called the Tome of the Hieroprince, which was continually read by at least one member, Umu Seven. Furthermore, the group commemorated a happening known as the Hieroprince's Ascension.
Alexander Freed referenced the Hieroprince in his 2015 novel, Battlefront: Twilight Company.