The backstory of Divine Divinity started in The Age of the Damned, with a group of wizards in Stormfist Castle being driven out due to the nature of their research, and the experiments they had started performing, with their leader killed by Duke Hark Ferol. The outcast wizards made a pack with demons in order to survive and, just as importantly, get revenge. Thirty years later they made their first attempt, with an army of demons and wizards. The Lord of Chaos was able to return to Rivellon in spectre form, though largely powerless. After four months the loosing allies in Rivertown were eventually forced to retreat to Stormfist castle, and would have been defeated if not for the timely arrival of an army of dwarves. A short time later (20 years?) the Demon of Lies was able to enter Rivellon in physical form, with a much larger army, and required the sacrifice of the Council of Seven in order to defeat (DD's 'The Prophecy' pdf). Divine Divinity was the start of the third attempt of the Lord of Chaos to return to that realm.
The Original Sin may be whatever those wizards were doing. They became the damned after making the pack with demons, and eventually developed into the Black Ring.
