Pontian succeeded Urban I as Bishop of Rome in 230 and governed for five years through the brief reign of Alexander Severus and the beginning of the Maximinus Thrax persecution of 235. His pontificate is principally significant for two unprecedented events.
First: Pontian was arrested in early 235 — along with the rival antipope Hippolytus, who had headed a schism against the Roman papacy since the reign of Callixtus I (217–222) — and both were sentenced by Maximinus Thrax to deportation to the lead-mines of Sardinia (the standard Roman judicial sentence ad metalla for socially-prominent capital convicts, intended as a slow execution-by-labour in the lethal Sardinian mining environment). On September 28, 235 — during the journey to Sardinia — Pontian formally renounced the papacy in order to allow the Roman community to elect a new bishop and to prevent the church from being left without effective governance during his coming death. This is the first formally documented papal abdication in church history, a thousand years before the more famous abdications of Celestine V (1294) and Benedict XVI (2013).
Second: in the Sardinian mines, Pontian and the antipope Hippolytus reconciled — Hippolytus formally ending the schism and rejoining the Roman Catholic community. Both died in Sardinia within months of each other (Pontian by mistreatment, Hippolytus probably similar). The bodies were returned to Rome by Pope Fabian (Pontian's successor) in 236, and the two were buried together. Their joint feast on August 13 commemorates their reconciliation in exile.