The Nag Hammadi Scriptures – Schools of Thought In The Nag Hammadi

No real group called Sethians. Term used by certain of the fathers of earl Christian church. 175-475CE produced writings refer to Gnostic groups the call Sethian.
Refer to Sethians in these texts as “the great generation”, “strangers”, “another kind”, “the immovable”, the seed of Seth”, the holy seed of Seth”, “race”, “seed”.

“And Adam knew his wife again and she bore a son and called his name Seth, for she said, God has appointed for me another seed…when Adam had lived a hundred and thirty years, he became the father of a son in his own likeness, after his image and named him Seth”

Seth is the supreme trinity. Father (Invisible Spirit), Mother (Barbelo) and Child (Autogenes). The spiritual seed as are descendants.