In Gnostic language, the demiurge refers to the "malevolent God" of the Old Testament (Yahweh), a fallen angel responsible for material creation. This is an evil force keeping human souls in a prison of matter while misrepresenting himself as the one God of all creation.
Boris Mouravieff speaks of the Absolute III when referring to a similar idea. This is also called the forces which govern the air, Lord of this world etc., i.e. the devil. Mouravieff is not, however, exactly a Gnostic; he is closer to Fourth Way thinking.