This ancient Gnostic writing probably came from a group called the Cainites. The only reason we know about it is because early Christian writers quoted from it, especially Bishop Irenaeus of Lyons. Because Irenaeus wrote about it in the second century AD, the Gospel of Judas must have been written before that time.
The text probably included secret teachings that Judas Iscariot was said to have received from Jesus. It may have summarized the “true” or “higher” knowledge that this Gnostic group claimed to possess. The gospel gives its own explanation of the “mystery of the betrayal,” saying that Judas’s actions made salvation possible for everyone. According to this view, Judas either protected the truth of Christ or prevented evil powers (called Archons) from stopping the crucifixion, which they feared would destroy their power.