Lucian the Divine the protagonist of the original game (Divine Divinity) who was "assassinated" by a Dragon Knight. But at the end of "Ego Draconis" it is shown that he is alive, but imprisoned in the "The Plane of Hypnerotomachia".
Lucian was a simple man at the beginning of Divine Divinity, however he was eventually blessed with incredible powers and status as a Demigod. Lucian fought against the Black ring and their attempts at Summoning the Chaos demon. His most Prominent victory was against the Leader of the Black ring, the Demon of lies. However, after he beat the demon he noticed the summoning had been successful and the Demon of Chaos had infected the young baby that was placed upon the Altar. Lucian knew he had to kill the child to save the world, but he could not bring himself to harm the small newborn so he adopted the child and named him Damian.
After his Victory against the Black ring and the demon of lies he became the exalted leader of Humanity and was praised as a God. Damian grew up at his father's side showing no signs of Chaos infection or evil thoughts. The black ring, however, found out about Damian and sent Ygerna to Damian to teach him about his powers. Lucian discovered Ygerna and her teachings and ordered her execution. It was Lucian himself who stood before Ygerna as the executor, he tried to make Ygerna forsake the Black ring and see what she did to Damian was wrong, but Ygerna would not listen; in the end Lucian struck, but unfortunately Damian walked in and cast a Soul Forge just as Ygerna's life ended. Outraged, Damian attacked his Father, but was forced to flee. Years later, Damian returned as the leader of the Black ring and once again attacked his father, but Lucian proved too much for the young man and he was rendered unconscious. Zandalor told that Damian was too far to be turned, but Lucian could not kill him. In the end he and Zandalor, with a heavy heart sent Damian into another dimension and hoped he would never return.
Damian, however, did return with the help of one of his Father's own Paladins and began his War against Rivellon. Lucian in the end stood as the victor and Damian was forced to retreat again, but in the hour of his victory a Dragon knight, charmed by Damian's power, stabbed the Divine in the back and he fell over dead.
This however was an illusion by Damian who had somehow managed to trap his Father in a Crystal prison and promised him he would see Rivellon burn and not be able to do anything to save it but watch. Lucian remained imprisoned for years as the world mourned the loss of their God. It was not long until he had new company however, the last Dragon knight was imprisoned in a crystal next to him and he explained everything to the Dragon knight about Ygerna and Damian.
The Dragon knight managed to flee the crystal prison with help from the specter of Behrlihn and promised if the Dragon helped him he would free Lucian as well. Lucian saw the Dragon Knight and Behrlihn return quite a few times, teleported in by Bellegar who tried to trap the latter once again. In the end the Dragon Knight returned but not by Bellegar's hand but Ygerna, now burned by the Destruction of the Black ring's Citadel; he pleaded with her to surrender but once again she ignored him and attacked the Dragon Knight. The Dragon was victorious and with Ygerna´s second death, Lucian was freed.
He was welcomed back to Rivellon in Aleroth by thundering cheers and a Dragon's roar.
He is mentioned many times in the game, mostly by praising him or praying.
He makes an appearance at the end of Ego Draconis by telling you that it was Ygerna who "advised" you, and not Talana. He also states that Damian is his son.
At the beginning of Flames of Vengeance he is warning you against trusting Behrlihn.
In the end of Flames of Vengeance he is liberated by killing Ygerna, and later exits the ministry and greets the people.