Complex sentence: Somewhat later this sect received new life and strength by the accession of a certain Severus Eusebius, "Historia Ecclesiastica", IV, xxix, after whom Encratites were often called Severians.
Split into simpler sentences: Somewhat later this sect received new life and strength by the accession of a certain Severus Eusebius, Hist. Eccl., IV, xxix, after whom Encratites were often called Severians.