This is an almost criminally oversimplified introduction to the concept, but it's a thing from the old "Gnostic" cosmologies, of which there were many mutually incompatible versions. The basic idea was that the creator of the material world is a "false god" that tries to keep souls trapped in the universe it's made and prevent them from obtaining enlightenment and escaping into their true spiritual home. Think some of the contemporary species of Indian mysticism, but with a malevolent "devil" figure presiding over the illusory world. For the most part, the Gnostics, including the Christian ones (there were others as well), seemed to also believe in the same basic concept of reincarnation-until-enlightenment-is-obtained.
In the Christian versions, often the Jewish god described in the Old Testament is itself regarded as the demiourgos, while Christ was an emissary sent to make mankind aware of the true god and guide us to salvation from our material prison. There is a fairly interesting version of the Garden of Eden myth which portrays Yhwh as the demiourgos trying to keep Adam and Eve confined in ignorance, and the serpent in the garden is actually suggested to be the first appearance of Christ, which leads them to the fruit of the tree of "Knowledge of Good and Evil", granting them an awareness of the true nature of their situation.
Gnostics did not seem to have much use for anything in the Old Testament, aside from some Psalms and about the first 60% of Isaiah.