Tatian the heresiarch.
Lives of Illustrious Men (De Viris Illustribus) · Saint Jerome
Tatian who, while teaching oratory, won not a little glory in the rhetorical art, was a follower of Justin Martyr and was distinguished so long as he did not leave his master’s side. But afterwards, inflated by a swelling of eloquence, he founded a new heresy which is called that of the Encratites, the heresy which Severus afterwards augmented in such wise that heretics of this party are called Severians to the present day. Tatian wrote besides innumerable volumes, one of which, a most successful book Against the nations, is extant, and this is considered the most significant of all his works. He flourished in the reign of Marcus Antoninus Verus and Lucius Aurelius Commodus.
ViriIll 1.31.2