The Demiurge, i.e., the Architect, the Artisan, the Creator, is a term describing the the god who fashioned the Universe and material existence, and who reigns over such creation. The term is used both in philosophy and in various religious sects, such as Gnosticism.
For most philosopher, the Demiurge is "number 2" on the totem pole of divinity and is the highest aspect of divinity mankind can comprehend. Behind the Demiurge lies "the one", the unknowable. It is this "unknowable" one that is, "The One, True God".
In Gnosticism, the Demiurge is usually portrayed as a false god who has imprisoned human souls in the false material world. According to certain Gnostics origins stories, an aeon named Sophia was the first to 'sin' by creating a being that should have never been. She did this without consulting with the other aeons. Her creation was the Demiurge. The Demiurge immediately attempt to take over and Sophia realized the gravity of her mistake and trapped the Demiurge within a black sphere or in other words, a false Universe. The Demiurge, unaware of it's fate, proclaimed itself to be the one true God and began to fashion it's prison to it's liking, creating the Universe that we see today. The Demiurge would go on to create human beings. However, the Demiurge did not create our souls but merely breathed into mankind part of his own "spark of divinity", which he was given by Sophia. Therefore, the Demiurge is referred to as "the half creator", as he created mankind's bodies but did not create our souls.
In Gnosticism, the Demiurge is generally viewed as an evil character that humans need to outwit and defeat before their soul can return to "the Source", our true existence. The Demiurge will try every trick in his book to keep humans trapped here in this fake universe. When a person dies their soul is reborn until one of either two things happens; 1.) The person learns to give up all desire and reaches a transcendent state so that they merge with the Source or Pleroma, or 2.) the spark within them finally goes out. If the spark of divinity goes out in the person then when that person dies they are completely obliterated. This obliteration is referred to as the second death.
Though the Demiurge is considered to be evil by man Gnostics, all hope for his salvation is not lost. It is believed that eventually the Demiurge will learn from it's mistakes and will likewise reach a transcendent state by which it will merge back into the Source.
To the Gnostics, the Demiurge was identified as the God of the Old Testament. The God spoken of by Jesus was not the Demiurge, but rather the "The Unknowable One", the true God.
What Is Gnostic Demiurge?