Viconia explains why she sent her agents out to find the prism. The Absolute, as a religion, was directly competing with Sharran religion for the same converts, and advancing in her religious territory, so to speak. She had been spying on this new cult and found out that they feared an artefact which they were desperately trying to find. So she had to find it before they did.
This implies that before Tav was even captured, the Cult of the Absolute had begin and was gathering followers. The way the story is layout this sounds like a major plot whole as it seems outside the timeline and factors we know of.
