I've only recently started reading the source material and I've learned that the Gnostics believe that the God in the Torah is actually an imperfect God (described as resembling a dragon) and not the true Father of everything. Jesus Christ's father is not the Torah God but the true Father of everything. Jesus Christ was trying to save humanity from the Torah God.
Seems pretty accurate to me. Many people say that jews worship the devil. Well, the Gnostics basically said the same thing in texts over 2000 years old. I've also heard the Torah God is a dragon bit before and thought it was a modern view. I didn't realize it literally was written in texts 2200 years old.
In Gnosticism, it was the imperfect Father who created us but it was an extension of the perfect Father that gave us life. Easily commingled as one Father who gave us both rather than separated out as the Gnostics do.
Demons are mentioned in the original Gnostic text I've been reading but I'd need to delve more into it to truly understand their purpose.
Gnosticism seems to have a different take on demons and demonic possession than most Christians understanding of the two; however, in practice the outcome is similar. Gnosticism suggests there are Archons (rulers of this world) created by the imperfect God who keep humans trapped in this material world. The way in which they keep humans trapped is by distracting humans away from the innate understanding of their divine spark. They do this by distracting humans with vices (so-to-speak) that a Christian would associate with demonic possession and these archons are describes by some as demonic (due to the commingling of religious theories). Gnostics wouldn't just believe in "demonic possession" as a Christian would understand it but they would go on to say it's a defining feature of the material world because it is through demons and demonic possessions the archons keep us trapped in this material world.
Essentially, the Father, the son and the invisible virgin spirit are the trinity in this context.
The resurrection is the reason the Catholic Church declared Gnostics as heretics. The Gnostics believe that Jesus did resurrect but as his true form which is "pure light".
"However, I saw someone coming near us who looked like the one who was laughing on the tree (cross). He was filled with the Holy Spirit, and it was the Savior. There was a great light surrounding them, indescribable light and countless angels blessing them... ...The one who was released is my incorporeal body. I am the rational Spirit, full of radiant light. The one you saw approaching me is the spiritual Fullness, uniting perfect light with the Holy Spirit in me... That is why I said, 'To everyone who has, more will be given,' and 'Whoever has nothing,' - which refers to the man of this world who is completely dead - 'will have everything taken away'. And if someone manifests from the immortal being, they think they will capture him; 'to him it will be given and will be taken from the one who is.' But you, be brave and do not fear anyone, for I will be with you so that none of your enemies will have power over you. Peace be with you; be strong." When the Savior had said this, Peter came to himself. The Apocalypse of Peter." - Apocalypse of Peter