When he and his sister turned fourteen, they were allowed to attend Luke Skywalker's Jedi Academy on Yavin 4. While there, Jacen developed an extensive collection of the jungle moon's exotic fauna, many of which escaped the cages built for them by Jaina. When he finally constructed his own lightsaber, Jacen chose focusing stones which produced a glowing, emerald green blade. He later trained directly with Luke himself, as Luke began moving the new Jedi Knights back to the pre-Empire style of teaching. Luke also trained Jacen's brother, Anakin, although both brothers had different ideas on what the future of the Jedi should be.
Jacen agreed with Luke, that the formation of a new Jedi Council would help bring the vigilantes under control. Jacen also believed more in the spiritual aspects of the Force, while Anakin held to the physical uses of the Force. They fought often, verbally and with lightsabers, both claiming their intense sessions were simply training.
He traveled with his younger brother to Centerpoint Station, just before the Battle of Fondor, but urged Anakin not to use the Force to fire the station's main repulsor. When Thrackan Sal-Solo fired it instead, and nearly destroyed the combined Republic and Hapan fleets, Jacen felt himself lost in his struggle to understand the Force. After having an intense vision of the galaxy, teetering on a single balance point that he alone controlled, Jacen tried to stop using the Force altogether. His family tried to bring him out of this mental state, but Jacen doggedly refused.
However, when his mother was threated by the Yuuzhan Vong on Duro, Jacen realized that he had reached the balance point in his vision. Drawing on the Force, he managed to escape with his mother and get her to safety. During the escape, Jacen badly injured the Yuuzhan Vong Warmaster, Tsavong Lah, earning him a position of hatred among the alien invaders. When the Yuuzhan Vong learned that Jacen and Jaina were twins - an event which was rare in Yuuzhan Vong births, and indicated an omen from the gods - both siblings were targeted for capture and eventual sacrifice.
Shortly afterward, Jacen and his siblings joined the Jedi strike team which was sent ot Myrkr to locate and destroy the voxyn queen. When Anakin was killed aboard the Baanu Rass, Jacen found that his sister blamed him for Anakin's death, despite the fact that Anakin gave specific orders to reach the queen. Eventually, the Jedi were able to defeat the voxyn queen, but Jacen was captured when Vergere betrayed him to the Yuuzhan Vong.
Despite her changing allegiance, Vergere provided Jacen with several of her healing "tears," to help prepare him for the torture he was about to receive after his capture. The rest of the strike team fled, vowing to rescue Jacen at the soonest possible moment. However, once in the Hapes Cluster aboard the Trickster, Jaina and the others received a wave of anguish through the Force that seemed to indicate Jacen's death. Jacen, however, had been taken aboard a Yuuzhan Vong seedship and secured in a modified Embrace of Pain by Vergere, as part of something known as the Solo Project. Vergere and Nom Anor hoped to turn him to the Yuuzhan Vong's True Way, and he was held in the Embrace of Pain for many months. Vergere, in an effort to eliminate his reliance on the Force, took away his link to the Force and forced him to recognize other ways of tapping into its energy. This was the "death" Jaina and other Jedi felt. Jacen began to understand the pain could eventually be overcome and used to his advantage, and that the Force was not simply black and white.
Vergere's lessons taught him that the Yuuzhan Vong existed in another facet of the Force's energy, and that there were more grey areas than Jacen had ever believed possible. Upon his release from the Embrace of Pain, Jacen discovered he was aboard a seedship, where he was bound as a slave to an immature dhuryam. Jacen developed a relationship with the future World Brain, and eventually discovered that he could tap resources within the Force that he never knew existed. When the tizo'pil Yun'tchilat occurred, Jacen chose his time to strike at his captors. Never truly turned to the True Way, Jacen tried to destroy the World Brains before one could be inserted into Coruscant's new environment. Vergere interferred, playing on his emotions to stop Jacen from killing the dhuryam which had become his "friend".
Jacen awoke to find himself on Coruscant, now renamed Yuuzhan'tar in honor of the original Yuuzhan Vong homeworld, along with Vergere. They were hunted by the warriors assigned to Master Shaper Ch'Gang Hool, and forced to accept the True Way. He then put into motion his next plant, to capture Ganner Rhysode. Ganner had been searching for Jacen, who lured him into the chamber of a camp ship and captured him. Once on Coruscant, Jacen subtly explained that he was working with the Yuuzhan Vong in order to gain their confidence. Then he planned to use the World Brain to act as his agent on Coruscant. Ganner gave his life to keep Jacen alive long enough to gain access to the World Brain, which had been the dhuyram he befriended. Jacen asked the World Brain to help him monitor the situation on Coruscant, then he fled the planet with Vergere.
Jacen later returned to Master Skywalker, who accepted his return and allowed him to return to work with the Jedi Knights. He tried to listen to Vergere's words and advice on the nature of his destiny within the Force, but when his sister Jaina was in danger during the Battle of Ebaq, Jacen blindly raced to her rescue. He was trapped by Yuuzhan Vong in the mines of Ebaq 9, and only Vergere's sacrifice allowed him to survive. He eventually reached Jaina, where they were attacked by Tsavong Lah. Jaina managed to defeat the Warmaster in combat, and the twins were rescued by New Republic forces. Jacen then commited himself to reconciling the Yuuzhan Vong with his definition of the Force, and vowed to honor Vergere's memory by working to fulfill his destiny. As part of this personal mission, Jacen agreed to accompany his Uncle Luke and Aunt Mara on a mission into the Unknown Regions, in a search for the planet Zonama Sekot. He had learned of the planet from Vergere, and hoped that his connection to her would help their cause.
Upon finding the planet in the Klasse Ephemora System, Sekot initially refused to help them. In a series of devious tests, the living part of the planet separated Jacen from Luke and tried to learn their true motives for coming to Zonama Sekot. Eventually, both Luke and Jacen convinced the planet they were seeking a peaceful end to the conflict with the Yuuzhan Vong. Sekot then agreed to accompany them back to the galaxy, in an effort to find a way to end the war. Upon reverting to realspace near Coruscant, Jacen found himself once again in the company of his family. Han, Leia, and Jaina had been dispatched to meet them, and the family was briefly reunited before returning to the war. Jacen and his sister accompanied their uncle Luke to the surface of Coruscant, in an effort to gain access to the Citadel and bring Supreme Overlord Shimrra to justice. Jacen was able to reach the mind of the World Brain which was controlling the planet, and was able to calm it down and put a stop to the destruction it was causing on the surface.
When the group entered Shimrra's throneroom, they were beset by a group of fifteen Slayers, and only Jacen's link to the World Brain allowed them any measure of success. When Jaina set out to capture Onimi, Jacen found himself facing the remaining Slayers, who had abandoned Luke so that Shimrra himself could destroy the Jedi Master. After Shimrra's defeat, Jacen left Luke in Mara's capable hands and set out to locate his sister, only to be assailed by Onimi. Jacen suddenly realized that Onimi was perhaps the most powerful of all Yuuzhan Vong, since he had managed to tap into the Force in a way that no other individual could. His own Shaping had somehow reconnected him to the Force, and gave him powerful abilities as a Shaper and as a fighter. Jacen was forced to fend off all manner of projectiles, then had to find a way to neutralize the poisons that Onimi created to kill him. Drawing on the power of the Force, Jacen understood that only a complete surrender to its energy would save him. In this state, Jacen was able to fight off whatever Onimi threw at him, realizing that he had finally found the truth about the Force and the way in which a Jedi should connect to it. He became simply a living conduit for the power of the Force, embracing neither good nor evil but simply existing within it. In this manner, Jacen was able to eradicate the evil and greed within Onimi, killing the Shamed One in the process.
With the Yuuzhan Vong surrender at Coruscant, the war was ended and the Galactic Alliance set out to restore as much of it as possible. Jacen decided to set out in search of other Force users - such as the Jensaarai, the Sunesi, and the Fallanassi - to deepen his already vast knowledge of the Unifying Force. This exploration allowed him to acknowledge the call of UnuThul but resist becoming a Joiner, when the Colony began its expansion in the Unknown Regions. He remained neutral in the growing conflict, hoping that the Force would guide him to a resolution. However, he experienced a terrible vision of the galaxy in flames, which left him without any clear path. Added to his confusion was the revelation that an evening spent with Tenel Ka at the start of the Qoribu Crisis had produced a daughter, which Jacen discovered about a year later.
While trying to piece all of this together, Jacen realized that the Force was calling on him to save his daughter - and the rest of the galaxy - from destruction at the hands of the Killiks. He then turned his efforts to eradicating the Dark Nest before it could launch the war he had seen in his vision. He agreed to accompany Jaina on a mission to disable Supply Depot Thrago, in an effort to provoke the Chiss into attacking the Colony, knowing that the Chiss had built up enough military power to defeat the Killiks. All the Chiss needed was an excuse to launch their attack. Jaina and Jacen were able to gather several Jedi together to launch the mission, but Jaina recoiled when she discovered that Jacen was also planning to exterminate the Colony to avoid seeing his vision come true. Jacen continued pursue any means necessary to ensure his vision didn't become a reality, including attacking a convoy of Colony ships that were traveling to the Nickel One asteroid.
Despite the fact that the Killiks were on a mission ot overthrow the Verpine government, Jacen had been forbidden to fire first by Master Skywalker. Jacen later accompanied Master Skywalker on his mission to eliminate Lomi Plo and cut off Raynar Thul from the Colony. In the Gorog nest ship over Sarm, Jacen was rendered unconscious when his StealthX crashed inside the ship. He recovered, but was stabbed in the abdomen by Lomi Plo's lightsaber. He eventually recovered from his wounds, and returned to Ossus with Master Skywalker.
Jacen later took on the task of training Ben Skywalker in the ways of the Force, when Luke discovered that Ben seemed to open up more to Jacen than anyone else. Jacen gladly accepted the task, and was able to help Ben come to understand his relationship to the Force. Jacen's own beliefs continued to evolve, and he came to understand that a Jedi could kill another being if it was deemed the right thing to do by the Force. When he and Ben were dispatched to investigate the Dammant Killers weapons facility on Adumar, Jacen found that he could kill the soldiers guarding a secret weapons production site, since they were dealing with violent customers and would become one with the Force after their deaths. This continuing adjustment in Jacen's view of the Force led him to have serious misgivings about the way his Uncle Luke was handling things, a belief that he only discussed with his parents.
His views were even more skewed when he and Nelani Dinn discovered that Brisha Syo was actually Lumiya. The female Dark Jedi tried to lure him into a position to become a benevolent Sith Lord, in the mold of Darth Vectivus. She provided an explanation that led to the conclusions that Luke had been corrupted by the light side of the Force, and that Vergere had actually been a Sith. She then explained that the dark man Luke was seeing in his visions was actually Jacen, after he accepted his fate as the next Sith Lord. Jacen allowed the Force to flow with her words, and suddenly saw a pathway that led to his killing of Master Skywalker. Realizing that he needed to avoid this possible future, Jacen understood that he had to eliminate anything that might lead up to it.
Unfortunately, one of the many individuals who nudged the future to this conclusion was Nelani, and Jacen ruthlessly stabbed her in the chest to prevent any trouble. After returning to Coruscant, Jacen came to believe that Lumiya was right, and that he needed to pursue the knowledge of the Sith. In all his travels, Jacen had learned a great deal about the Force, and the only gap in his knowledge was an understanding of the ancient Sith lore. Thus, he came to realize that he had to accept Lumiya's offer of training. In the meantime, though, Jacen became involved with the Coruscant Security Force when Corellian terrorists began attacking non-military positions on Coruscant. His ability to tap into the Force gave him an edge in tracking down insurgents, as did his connection to the World Brain on the planet. Thus, he was the perfect choice to lead the newly-formed Galactic Alliance Guard, a move that brought a promotion to Colonel as well as the consternation of both his parents and the new Jedi Order.
His fall toward the Dark Side was precipitated by several events, including his beating and killing of Ailyn Habuur while using a Force technique to coerce her during an interrogation. This event gave Ben Skywalker and Lon Shevu a reason to doubt Jacen's intentions, and caused his father to turn his back on Jacen, claiming that he no longer knew who his son was. As his father left him on Corellia, Jacen realized that his destiny was with the Sith, but he vowed not to fall into the same traps that led to his grandfather's transformation to Darth Vader. He vowed to use his powers for the good of galaxy. For reasons unknown, Jacen began wearing a flowing black cape, instead of the normal brown cape of the Jedi, which made him appear more and more like Vader.
When he learned that an assassination attempt had been made on the life of Tenel Ka, Jacen was able to put enough pieces together to link the assassination to the Corellian insurgents, and secured the use of the Anakin Solo before traveling to Hapes. There, he found himself ordering the Star Destroyer's crew to fire on the Millennium Falcon, after hearing of the presence of his parents at the assassination attempt. Jacen felt no remorse at nearly killing his own parents, a fact that didn't escape the notice of Luke Skywalker or many of the other Jedi.
Jacen's reputation as a galactic hero was heightened in the wake of his assistance in defending the Queen Mother from the Heritage Council's treacherous plans, giving him even more power within the Galactic Alliance. However, with this power and fame came dreams of his own mother sacrficing her own life to ensure his death, and only the recognition of the fact that he could sacrifice any member of his family in order to ensure the safety of Allana gave him any solace.
Jacen continued to pursue the path of the Sith, while trying to maintain the image of the loyal leader of the Galactic Alliance Guard, but he continued to harbor reservations about the way in which he was to achieve a level of mastery over the Sith way. According to Lumiya, he was going to have to sacrifice someone he loved. He feared that this person might be Tenel Ka or Allana, but in the wake of the Battle of Gilatter Eight, he came to understand that he might have to sacrifice one or both of this parents in order to achieve his destiny. Upon returning to Coruscant, however, Jacen's concern about the Prophecy bacame directed at Ben Skywalker, whom Lumiya had deemed too weak to serve as Jacen's apprentice in the wake of his mission to recover the Amulet of Kalara.
Jacen's control of the Force continued to grow, to the point that he could permanently close down his presence in the Force, making himslef virtually invisible to other Jedi Knights. This was of no small concern to Luke Skywalker and the other Jedi Masters, although this concern turned to fear when Jacen taught the skill to Luke's son, Ben. For his own part, Jacen remained protective of his apprentice, and grew angry with Lumiya when she set Byalfin Dyur and his thugs on the young man's trail during the search for the Amulet of Kalara.
During this time, Jacen discovered a wealth of new information about the inner workings of the government from his administrative droid, HM-3. The droid showed Jacen how to subtly amend the laws in ways that gave him unprecedented power and control, and Jacen took advantage of them. He first had HM-3 craft the Legislative and Regulations Statute Amendment, which gave the leaders of the Galactic Alliance the ability to alter laws as they saw fit, provided that the changes kept the government within its budgetary constraints. It also provided Jacen with a way to amend the law enough to give him the right to remove any individual he believed could pose a genuine risk to the Galactic Alliance, a law that he invoked after learning that Cal Omas had been secretly dealing with Dur Gejjen.
He dispatched Ben Skywalker and a pair of GAG agents to Vulpter to assassinate Gejjen, then confronted Omas when he returned, having him jailed for attempting to undermine the laws of the Galactic Alliance. Thus, Jacen found himself and Cha Niathal in control of the government, with the rest of the galaxy under martial law until the crisis could be averted. He assumed the role of Chief of State, even though Niathal had Omas' office sealed until the end of the crisis.
As the need to make his sacrifice and complete his Sith training drew near, Jacen became aware that the sacrifice could have been any number of people he cared about. He made a secret trip to Hapes to see Tenel Ka and their daughter, Allana, and was unaware that he was followed by his aunt Mara, Lumiya, and Ben Skywalker. Mara revealed herself first, setting off a starfighter duel in their StealthX ships. Lumiya arrived later, using her Sith Meditation Sphere to damage Mara's ship and force her to land on Kavan.
On the remote world, Jacen found himself in a struggle for his life. Mara used the tunnels and ruins to her advantage, ambushing Jacen and shattering his right knee. As he went down in pain, Mara drew her blaster and fired at him. Unwilling to die then, Jacen drew on the Force to deflect the blaster bolt and injure Mara with the rubble it created. After a brief struggle, Jacen managed to take a poisoned dart from his belt and jab it into Mara's leg. She died swiftly, creating a shift in the energies of the Force that Jacen knew would bring Luke Skywalker to hunt him down.
Jacen fled to Ziost, where he was reunited with Lumiya. Lumiya agreed to intercept Luke and make him believe that she had killed Mara, while Jacen returned to Coruscant to resume his ascendance. Jacen returned to Kavan, where he helped Ben recover his mother's body, and vowed to help Ben locate Mara's killer. In his heart, Jacen realized that the prophesy of "immortalizing his love" had not meant that Jacen would have to kill someone he loved. Instead, it meant that he had immortalized Ben's love - that of his own mother - and that it would plant the seeds for Ben to become a great Sith. It was then that he realized that his journey was complete. Jacen accepted his fate as a Sith Lord, becoming known as Darth Caedus.
Jacen spent the following weeks consolidating his power and struggling to keep his role in Mara's murder a secret. He was confronted by his former apprentice, Ben Skywalker, who firmly believed that Jacen was the killer. He also found himself under intense scrutiny from Luke Skywalker himself, although the Grand Master of the Jedi did not immediately accuse Jacen of the crime, even after Mara's body disappeared into the Force when Jacen suddenly appeared at her funeral.
In the aftermath of the funeral, Jacen was confronted for allowing GAG soldiers into the Jedi Temple, on a mission to capture his own parents. Jacen explained that he had received word of a possible Bothan bombing attempt, and that he had every right to track down the "terrorists" his parents had become. Jacen also spent several weeks coming to terms with his new title, and struggled consider himself solely as Darth Caedus. This belief continued when Jacen learned that his parents were being harbored by the Wookiees on Kashyyyk, and was enhanced when Grand Master Skywalker defected the Jedi Order from the Galactic Alliance and fled to Kashyyyk.
His fall toward fully becoming Darth Caedus culminated at Kashyyyk, where he launched an unprovoked attack on the planet, then was forced to confront Master Skywalker in combat. Jacen was badly injured in the fight, having been soundly defeated by Luke and then suffering a vibroblade injury from Ben, but used his pain and anger to shed his old identity and accept his role as Darth Caedus.
Some info gathered with permission from:
The Completely Unofficial Star Wars Encyclopedia
