What is "sethianism"

The Sethians were a Gnostic sect during the Roman era. Alongside Valentinianism, Sethianism was one of the main currents of Gnosticism during the 2nd to 3rd centuries. Their thinking, though it is predominantly Judaic in foundation, is arguably strongly influenced by Platonism. Sethianism attributed its gnosis to Seth, third son of Adam and Eve and Norea, wife of Noah (who also plays a role in Mandeanism and Manicheanism).