St. Pontian was elected pope in the year 230. Five years later, he was exiled to the mines on Sardinia, an Italian island, during a period of persecution against Christians. He resigned from his papacy, and died as a martyr.
St. Hippolytus was a priest and theologian, but he rebelled against the Church in 217, during the papacy of Callistus. He was exiled to the Sardinian mines with Pontian, who brought him back to the faith. Hippolytus also died a martyr.