>>10637
Haven't read for years so might be a bit iffy about this, but here goes.
Basically put Jacen gets a crisis of conscience sometime after the Vong War, as a result of increasingly vague understanding of reality and morality due to his vongsense and mindfuckery by Vergere. Something something not understanding the force enough something something need to broaden horizons. A lot of jedi do a lot of soul searching during that war. So he goes off on a quest to learn alternative force theologies, kinda like a space Leonard Cohen going to space scientology meetups and space taoist temples.
The side effect of this quest is that Jacen gets an increasingly ambiguous view of morality and the force, having learned from as varied groups as the dark witches of Dathomir to the morally ambiguous Jensaari, to the cult of the Theran Listeners and the crazy old Fallanassi. Note that Jacen had basically saved the galaxy from the Yuuzan Vong and the Vong from the galaxy, and at this point STILL considered himself a student. The guy had a pretty big hard on for still being insignificant and weak, which ended up having the same effect as if he had been overly power hungry and ambitious, to seek more and more knowledge and skill. I think he also learned from the Kel Dor force cult, can't remember their name but they specialised in electricity or something. He increasingly became focused on these teachings in the hopes of being able to save the galaxy (which really was the only life he knew) such that the Fallanassi were suspicious of him and felt he had a darkness within him (their order was around balance, they would contentedly watch the galaxy burn if it was what was meant to be while Solo just HAD to save everybody).
Then the swarm war comes, and things get more and more morally ambiguous. Solo starts taking more and more aggressive action and seizing more and more power to help him get into places where his talents can help.
Some stuff happened after dark nest crisis but eventually Solo sits down and talks with a Sith Lady called Lumiya, who openly offered to teach him sith techniques that he could used in a manner detached from the dark side of the force in an attempt to bring peace. Solo saves this sith lady from another jedi, who Lumiya then agrees to allow her to take Lumiya into custody, Solo has a vision of what happens in that timeline (ends with him killing Luke Skywalker, lots of fucked up shit happening) so he kills Dinn and kills her for THE GREATER GOOD.
Things basically go downhill from there, but to the end Jacen is doing things for the sake of the greater good. His story is basically one of selfish selflessness, that he did terrible things for the sake of a stable galaxy (his own selfish desire).
Oh, he also got to mindfuck tahiri by making her addicted to visions of his little brother. Also, his twin bond returned right before he died, letting him warn Tenel Ka, and he let himself be struck down, refusing to kill his sister in revenge for his fatal wounds at her hands.
I missed a lot for the sake of brevity and probably got a few details wrong, but that is a very rough explanation of his messiah complex and how he fell.