Tatian and the Diatessaron

Tatian was a disciple of Justin Martyr, but after Justin's death he was influenced by gnosticism and started his own sect, called the Encratites.

He wrote an Address to the Greeks, which is orthodox; however, he is most famous for his Diatessaron, which is a harmony of the Gospels, the earliest testimony to the text of our four Gospels. He wrote it after his influence from gnosticism, though, so he left out all the parts where the Gospels emphasize Jesus as a physical. Gnostics believe that all material things are bad, so the Christ couldn't really have been fully human.