Millenarian Maths and the Third SackEdit
The Third Sack was triggered by Saecular fears of Thousanders possessing supposed "magical" abilities. These fears were encapsulated in the legends of the Incanters and the Rhetors, which first took hold c. A.R. 2700. Although these fears are initially discounted by Fraa Erasmas the arrival of the Daban Urnud triggers events which make this power evident as the Thousander Fraa Jad is able to shift his consciousness between cosmi and affect that of others in the Arbran cosmos. As an awareness of the powers of the Thousanders emerged, an unusual occurrence from the years just prior to the Third Sack, when a dinosaur skeleton suddenly appeared in the concrete of a new parking garage, is seen as a failed experiment in shifting cosmi.
The trauma of the the Third Sack was detected by the consciousness of the Urnudian commander, prompting him to order the Daban Urnud to proceed on a trajectory he believed would send him back in time, but instead led to a different cosmos. It is unclear if the flow of information from Arbre during the time of the Third Sack was deliberate or a byproduct of the trauma of that period.
The only maths which survived the Third Sack were three Millenarian maths, the Three Inviolates, which were protected by the Saecular power at the time because they contained stored nuclear waste. Genetic manipulation is practiced by Thousanders in order to protect them from the effects of dangerous radiation, which has the side effect of greatly increasing their lifespans.
At the start of the novel, it is generally believed, even by other avout, that the "thousand-year" commitment of the Milleriarians is just a poetic way of saying "in for life," and that the Millenarians do not actually live a thousand years. When Jad drops hints that he is significantly older than 100 years, Arsibalt and Erasmas initially don't believe him.