In the original Divine divinity Damian was a baby that was taken by the demon of lies to be the vessel of the Chaos demon. Lucian the Divine stopped the Demon of lies and was about to kill the baby to stop the chaos demon, but he couldn't bring himself to strike the helpless Damian, so he took him under his wing and raised him as his son.
Many years later the Black Ring sent the dark sorcerer Ygerna to teach Damian about the powers hidden away in his soul and she started to tutor him to awake his dormant demon and the two fell in love. Alas, Lucian found out about Ygerna and was about to execute her. Unfortunately Damian walked in as the blade fell and cast a Soul forging on Ygerna just as the blade hit, reversing the nature of the spell. Damian in a fury took control of the Black ring and attacked Rivellon, but Damian was only focused on his Revenge and so in the Temple to the divine he meet Lucian and attacked. Lucian however had prepared a trap for his son, a rift gate. Damian Paid no heed to the trap and stormed the Divine and the trap was sprung. Lucian stepped into the rift aswell to make sure only when he or one of his Paladins willed it, then it would open again. Lucian and Damian battled across the Dimension of nemesis only to see Lucian as the victor, however once again he could not bring himself to hurt Damian and therefore left.
Damian spend the next many years in Nemesis trying to find a way back to Rivallorn,with the help of the native species there, who like Lucian, had adopted him and was teaching him their ways. Damian with his lust for power however used a imp to steal a stone protecting Nemesis from Demons and therefore brought forth the race's doom.
Damian still hadn't found a way back yet though, but little did he know fate was about to smile to him. Damian met a paladin who had been trapped in the ethereal dimension aswell and tricked the hero into believing him a Death Knight, using the helmet of the Death Knight to cower his true identity and Tricking the Demon Overlord Samual to soulforge him to the paladin, making sure the paladin was forced to help him. they fought their way though Nemesis and in the end the paladin did exactly what Damian had hoped for. Damian was free and in return spared the paladins life and ended the soul forging between the pair. Damian returned to Rivellon and took control of the devious Black ring once again. and thus he started a new war against Rivellon that ended in his second defeat, but also in Tragedy for the people of Rivellon. In the war a Dragon Knight stabbed Lucian the Divine and rumors of his death spreaded across the earthrealm. This, however, was an illusion created by Damian and instead of killing his father he had him trapped in a crystal prison to Observe when Damian's Black ring was ready once again to scorch Everything Lucian held dear and leave only ash. Why he decided to leave his Father alive is yet unknown.
By the events of Ego:Draconis, Damian has once again begun his invasion of Rivellon, where he is first seen at the fore of his armada. The next time he is seen is immediately after the slayer becomes a Dragon Knight, where he threatens the Knight against continuing his quest.
The last time he is seen is at the end of Ego:Draconis, where he greets the now-revived Ygerna and assaults the Orobas Fjord port.
At the end of Flames of Vengeance, Ygerna reveales that Damian was not in his palace but somewhere else, working to unlock his full demonic powers.