— THE GARDENER

And he could finally recognize that the boy he had been, the optimistic, joke-spinning, animal-loving, kidnap-prone Jedi boy, was dead, slain on the same mission that had claimed his brother, Anakin. At last, understanding what had happened, Jacen did not miss his younger self.

independent and private rp blog for Jacen Solo of the Star Wars franchise, EU / Legends timeline default, written by Hope ( she / they ), 18+

— CARRD

  Let me start this by underlining the fact these changes happen over a span of 14 years and none of this happened over night ( which seems to be something the fandom often accuses the writers of for some reason ). Jacen wasn’t born bad and he was a good person for the first +20 years of his life but his fall to the dark was a long time coming by the time it happened officially in 40 ABY. 

   Most of Jacen’s bigger troubles obviously started with his imprisonment and torture at the hands of the Vong in 27 ABY when he is 18 years old. The Vong and Vergere especially break Jacen over the course of a whole year. He is isolated often, tortured almost daily at first and CONSTANTLY confronted with Vergere’s mind games. Three things happen at the same time here: Jacen is dealing with losing trust in the animals that used be his friends ( thanks to the Voxyn ), losing his humour after being forced to face horrible things and suffering the loss of his younger brother Anakin — and Anakin's death especially proves to be one of the WORST things Jacen experiences as he cannot escape the reminders of what it was like to see and feel Anakin die; first in traitor:

Remembering Vergere brings him to the voxyn queen, and the voxyn queen sends him slithering back down a despair-greased slope to Anakin's corpse. Anakin's corpse floats on a burning lake of torment far deeper than anything that can happen to Jacen's body.

     and then years later during exile:

But Anakin had been fatally wounded on this mission. Had died. The children of Han Solo and Leia Organa Solo had suddenly gone from three to two. Had suddenly stopped being invincible, invulnerable, immortal. Suddenly there was no room in his life, no room in his universe for humor. And from that time on animals had all seemed to wear the faces of voxyn. They were no longer his friends.

    In an instant, Jacen loses the things that made him him and goes through yet another identity crisis, a desperate search to figure out WHO he really is, a search that has marked his entire childhood already and has become a frustrating never ending cycle for him ( and would go on to influence him into accepting the name and identity of Caedus years later ).

   In the first few months during his imprisonment he tries holding onto his teachings, onto the knowledge that he cannot allow himself to fall into the dark but then he feels another thing adding to the pain he already experiences: He feels his TWIN edging closer to the dark in despair and he shares her rage through the twin bond, a bond he decides he has to ignore eventually to safe her from the pain he is feeling:

But he cannot let himself touch [Jaina] through the Force; he cannot ask her to share his torment--she is in so much pain already that to suffer his would only drive her darker yet. And so even his twin bond has become a source of anguish.

    Jacen has always been a very lonely person and mostly shared his emotions with his sister and no one else, not even his own parents. This moment is one of the first that marks a long history of decisions that eventually tore the twins apart and pushed Jacen closer to the dark. They both start trying to keep each other out of the bond to avoid HURTING the other further and end up isolating themselves in the process. Jaina eventually recovers from this, Jacen does not. Jacen goes on to shoulder all of his torment on his own starting with his torture at the hands of Vergere and ending with his guilt over what he believes he has to do as Caedus years later.

   The year Jacen spend with Vergere very much completely broke apart his view on the world and himself. Vergere declared Jacen Solo is dead and then proceeded to form Jacen into what she WANTED him to be. A man of action, someone who made decisions, something Jacen has been struggling with his entire life. During this time Jacen goes from considering her his jailer and torturer, wanting to kill her ... to considering her a supporter, a friend. It is a very concerning change Jacen goes through as he starts to ACCEPT Vergere’s philosophies. One specific lesson from her eventually becomes a horribly twisted foundation of Jacen’s own ideology:

"What distinguishes a flower from a weed is only-- and exactly-- this: the choice of the gardener."

   Vergere wants Jacen to make the choice, BE the gardener who decides who is a flower and who is a weed. At first Jacen is dedicated to proving her wrong, to showing her everyone is a flower, that he will save everyone, kill no one. The longer he is trapped alone with Vergere the less he can hold onto that belief and eventually this argument between him and Vergere finds its climax in Jacen killing a group of Vong in pure anger, an action she chastises him for while not offering him a BETTER way of releasing his anger, resulting in Jacen being trapped in a loop of knowing there is darkness in him and struggling to find a safe outlet for it, further fueling his already at times incapacitating paranoia.

   All of what Jacen experienced during his year away would go on to shape his view of the world forever and not always in a good way although it must be said he has possessed traits that affected his philosophies negatively from the start; most notably his stubbornness and pride:

Mara's look turned grave. "We must help [Jacen]," she said. "If he'll let us. He hasn't always been cooperative that way."

    And this conversation between Luke and Mara marks one of Jacen’s worst habits: His reluctancy to accept any kind of HELP. Jacen has always, always struggled with his pride, with the idea that he knows what he is doing. This kind of thinking almost got him killed at the start of the war and it would continue to get him into trouble many years later when he starts making decisions over people’s heads because he ‘ knows whats best ’. It becomes the most defining trait of his work and his thought process, the idea he knows what is best for EVERYONE. The more he slides into the dark the worse his arrogance becomes. 

   At first he mainly got himself into trouble with this kind of thinking but we see very soon after his return from captivity that he has learnt the WRONG lesson from Vergere as he uses the force to see into Tahiri’s head without her permission to try figure out what is bothering her. He acts out of a good reason ( trying to help Tahiri find peace and making her feel like part of the family ) but goes about it in a terrible way and justifies it to himself as a reasonable action and THAT becomes an ugly theme in Jacen’s actions later on.

   Jacen’s belief that he is always right has good sides and bad sides. He insists the war with the Vong has to end PEACEFULLY and it does thanks to his help but his success in this situation only further fuels his idea that the force is guiding him and that means he cannot be wrong. He goes on his five year journey and returns home early when the ‘ force ’ tells him to go despite his teacher insisting he shouldn’t abandon his studies early or risk having to deal with the consequences. He ignores the order and his own twin to go through with a war that he is CONVINCED is going to stop a bigger disaster down the line, all because he had a vision about it and at this point he has allowed his ego to become so big that he blatantly ignores anyone trying to talk him out of his ideas. 

    His five year journey that follows the war with the Vong is driven by the desperate need to find out once and for all who he really is and what his purpose is. It is important to note that his journey didn’t set off his development into Caedus, if anything it only made it easier for him to further fall back into ALREADY established bad habits such as letting his fear guide him and putting his pride and search for identity over everything else. Jacen didn’t return from his journey suddenly a changed man. The foundation for this change had already been laid YEARS prior thanks to Vergere and the struggles he dealt with long before he even met Vergere. 

    Things take an even darker turn when Jacen’s daughter is born. Jacen loves his daughter, more than anything else and when she is threatened by Tenel Ka’s grandmother and her people, who want a week old child dead, Jacen lets his anger guide him and lashes out, putting a brutal end to the attack on his daughter and first mind rubbing Ben so he won’t be able to accidentally reveal anything about Allana that could put her in danger and then almost killing Ta’a Chume for raising her hand against the girl. Jacen JUSTIFIES his behaviour ( both to himself and Tenel Ka ) as necessary, as almost too nice a reaction to such despicable behaviour. Tenel Ka doesn’t exactly discourage him, being worried for their child herself and with the two of them being the only people to know about Allana and her parentage, there is no one to disagree with them, to make Jacen see that he went TOO FAR and is on a dangerous path straight to the dark side now. His constant worry over her also helps make his paranoia much, much worse over the next few years.

    By the time Jacen’s family realises his behaviour has become incredibly worrying it is already too late. Jacen has already decided they’re wrong, he is right and that is how it has to be. Afraid to lose everything ( his daughter, his identity, his pride ... ), Jacen REFUSES to admit he is wrong and with years of only himself and at best Tenel Ka and at worst Vergere ( and eventually Lumiya ) being there to judge his actions ... he passed the point of no return years ago.