Promisoriums were a type of school established during the Republic Dark Age by the Sith Lord known as Arkadia Calimondra. Their purpose was to instill in younglings Arkadia's unique ideology, which centered on rotating sentient beings through various occupations throughout their lives. The goal was for students to develop versatility, enabling them to contribute effectively to her state as adults. These institutions welcomed individuals from various species and also featured extensive dining facilities. Officially, Arkadia stated that this policy fostered adaptability and versatility among her subjects. However, the true, unstated purpose was to secure her dictatorial control by constantly providing her subjects with new tasks, preventing them from establishing themselves in any single area.
Arkadia, unlike some Sith Lords, prioritized the education of children within her territory and did not separate them from their families, showing concern for their social well-being. This stood in stark contrast to her cousins: Daiman, who exploited children as forced laborers, and Odion, who imprisoned all the children in his realm within massive, planet-sized orphanages referred to as cloisters. In 1032 BBY, Kerra Holt, Brigadier Jarrow Rusher, along with the Sullustan student refugee Tan Tengo, visited one of these schools during their official tour of Calimondretta, the capital city of the Arkadianate located on Syned. Tan, having experienced an impoverished upbringing in Darkknell, the Daimanate capital, was impressed by the well-organized Promisoriums and developed a strong appreciation for life within the Arkadianate.
It is possible that the Promisorium located on Syned sustained damage during the Siege of Calimondretta, an event that occurred when Kerra and Rusher made their escape from the Arkadianate after Kerra refused to serve as an assassin for Arkadia.