The Pseudo-Clementine articles:

The father of this Simon is called Antonius, his mother Rachel. By nationality he is a Samaritan and comes from the village of Gittha, which is six miles distant from the capital. During his stay in Egypt he acquired a large measure of Greek culture and attained to an extensive knowledge and ability of magic. Then he came forward claiming to be accepted as a mighty power of the very God who has created the world. On occasion he sets himself up as the Messiah and describes himself as the Standing One. He uses this title since he is immortal and his body cannot possibly fall a victim to the germs or corruption. He also denies that the God who created the world is the highest, nor does he believe in the resurrection of the dead. Turning away from Jerusalem, he sets Mount Gerizim in its place. In the place of our true Christ he shows himself as the Christ. The content of the law he interprets according to personal ideas. He speaks indeed of a future judgment, but he is not serious; for if he truly believed that God will call him to account, he would not have turned against God Himself. Many do not know that Simon uses piety merely as pretence in order to steal secretly from men the fruits of truth. They believe in him, as though he were himself pious, in his manifold promises and in the judgment he had promised.

Simon's contact with the tenets of religion came about in the following way. There appeared a certain John the Baptist, who was the forerunner of our Lord Jesus. And as the Lord had twelve apostles, so also John had thirty eminent persons. Among these was a woman named Helena. Of these thirty Simon counted with John as the first and most distinguished; and indeed he was prevented after the death of John from assuming the leading place for a reason which we shall hear directly. John was put in prison at the very time when Simon had journeyed to Egypt to study magic. Therefore a certain Dositheus, who aimed at becoming the head of the school, was able to spread abroad a false report that Simon was dead and to take over the leadership of the sect. When now a little later Simon returned, he did not, on meeting Dositheus, demand of him his post, much as he desired it for himself, for he knew quite well that the man could not be removed of his office against his will. For this reason he made a pretence of friendship and for a while rested content with the second place after Dositheus.

When, however, after a time he met his thirty fellow disciples, he began to circulate slanders against Dositheus. This man, he asserted, hands down the doctrines incorrectly, and does so less because of an evil intent and more out of ignorance. Dositheus observed that Simon's well calculated slanders were shaking his own standing among the great multitude so that they no longer regarded him as the Standing One; then on one occasion when Simon arrived for the ordinary meeting, Dositheus struck out at him with indignation. The stick seemed to go through Simon's body as if it were smoke. Dositheus shouted to him out of fear, "If thou be the Standing One, I also shall pay homage to you." As Simon answered in the affirmative Dositheus, knowing that he himself was not the Standing One, fell down and did homage to Simon and, associating himself with the twenty-nine others, set Simon in his own place. Then Dositheus died a few days after Simon had attained the leadership but he himself had suffered downfall. Simon then took Helena to himself, and since then he moves about with her and up to the present day, as you yourself see, he upsets the people. Of Helena herself he asserts that he brought her down to the world from the highest heaven, of which she is the mistress as the mother of all being and Wisdom. Because of her, he says, there came about a conflict between the Greeks and the barbarians; although they clung only to an image of the reality, for the true Helena dwelt at that time with the supreme God. He deceives many in a plausible manner, by giving this new interpretation of the Greek legend, and at the same time he performs numerous wonderful deeds, by which we would have been taken in, if we did not know that he works them only by sorcery …

He has also burdened himself with blood guiltiness and has even related among his friends that he separated the soul of a boy from its body by means of secret magical invocations. He keeps the soul in the interior of his house, where his bed is, to assist him in his performances, having in this connection drawn a likeness of the boy. This boy, he asserts, he at one time fashioned out of air by a divine transformation and then, having put his appearance on record, he returned him again to air. That came about in the following way. In his way of thinking the human spirit, which tends to what is warm, first imbibes the surrounding air in the manner of a cucumber and sucks it in; having infiltrated into the interior of the human spirit, this air then changes into water. Since now the water in the human spirit cannot be drunk in consequence of its consistency, it has to undergo a transformation into blood. Let the blood coagulate and the flesh is fashioned. Then the flesh becomes solid, and so man comes into being not from the earth but out of air. And so Simon persuaded himself that in such a way he had been able to fashion a new man; of him he asserted that he had returned him to air, having reversed the changes that had taken place.

Eusibius adds in his Ecclesiastical History 2:13

Simon, a Samaritan of the village of Gitto, who in the reign of Claudius C'sar performed in your imperial city some mighty acts of magic by the art of demons operating in him, and was considered a god, and as a god was honored by you with a statue, which was erected in the river Tiber, between the two bridges, and bore this inscription in the Latin tongue, Simoni Deo Sancto, that is, To Simon the Holy God. And nearly all the Samaritans and a few even of other nations confess and worship him as the first God. And there went around with him at that time a certain Helena who had formerly been a prostitute in Tyre of Phoenicia; and her they call the first idea that proceeded from him." Justin relates these things, and Iren'us also agrees with him in the first book of his work, Against Heresies, where he gives an account of the man and of his profane and impure teaching.  We have understood that Simon was the author of all heresy.

For more information see the Early Church Fathers.