P3X-421 is an isolated desert world populated by simple people living in tents similar to desert nomads. Dr. Lindsay, an anthropologist from the SGC, had been working with the human population of the planet, hoping to ease them over the loss of their former false god during Goa'uld occupation. When a Prior stepped through the gate of P3X-421 and began spreading the religion of Origin and using miracles to prove his claims, it marked the first arrival of a Prior in this galaxy, and it was seen at first by the SGC as simply one of the expected number of opportunists taking advantage of sheltered civilizations by trying to fill the void left by the Goa'uld. Mitchell and SG-12 investigated the situation on the planet and confronted the Prior, who recognized Earth as the home of Daniel Jackson, from whom "we learned of your need for the revelation of your destiny." Mitchell and SG-12 returned to the SGC with the Prior, who responded to questions only in the vague rhetoric of the Ori before he burst into flames and vanished.
Cross Reference: Dr. Lindsay, Ori, Prior
Episode Reference: Origin