The cathedral ships were used by the Pius Dea to subjugate alien worlds during the Pius Dea crusades. Due to a culture of nepotism and patronage within the Pius-Dea controlled Republic bureuacracy, they were commanded by missionaries and manned by descendants of Republic Navy crew who had joined the sect. By the 11,500s BBY, the cathedral ships had become essential to the Republic's new network of Ordnance/Regional Depots along the Rim Frontier.
At the end of the Crusades, many ships were hit by a rogue navicomputer code developed by the Bureau of Ships and Services and randomly jumped into hyperspace, becoming stranded in interstellar space. This navicode also disabled their navicomputers, supralight engines and communications systems. Unable to restart their hyperdrives and re-enter realspace, many of the Pius Dea crew trapped aboard perished from starvation. Remaining ships were defeated by Renunciate battleships and the Pius Dea rule came to an end.