Following their adventure on Stygeon Prime, the rebellious crew aboard the Ghost embarked on a quest to find and eliminate a potent kyber crystal in the possession of the Galactic Empire. To pinpoint its location, the rebels needed an Imperial code breaker sourced from the office of ISB Agent Kallus stationed at the Imperial Headquarters on Lothal. To gain entry to the complex, Ezra Bridger received the assignment of infiltrating the Imperial Academy situated below, with the goal of pilfering the code breaker. He spent several weeks within the academy's walls, undergoing training by the Imperial Army during this period. Ultimately, he discovered the code breaker and successfully stole it, aided by fellow cadet Zare Leonis, who harbored rebel sympathies due to the disappearance of his sister, cadet Dhara Leonis, from the academy.
Bridger handed the decoder to his fellow rebels, enabling Kanan Jarrus and Hera Syndulla to navigate to the kyber crystal's coordinates. Subsequently, the Spectres passed the decoder to Leonis' girlfriend Merei Spanjaf, who required it to access confidential ISB files concerning Dhara. During this period, Bridger remained behind with the intention of rescuing fellow cadet Jai Kell, who faced peril from the Grand Inquisitor after displaying indications of Force sensitivity. Leonis and Kell seized an All Terrain Defense Pod to provide support for their escape, and the trio successfully exited the academy before the Inquisitor's arrival. Bridger and Kell escaped, while Leonis stayed back to gather more details about his sister, under the official guise of attempting to apprehend the other two. Concurrently, Jarrus and Syndulla located the Imperial convoy transporting the kyber crystal and destroyed it. Following the mission's conclusion, Bridger returned to the Ghost, Kell sought refuge in hiding, and Leonis was brought before the Inquisitor to provide information about Bridger.
Approximately five years prior to the Battle of Yavin, the Spectres launched an operation to intercept an Imperial convoy transporting a powerful kyber crystal. To pinpoint the crystal's location, the rebels had to procure a ZX-5 decoder from the office of ISB Agent Kallus stationed at the Imperial Headquarters situated in Lothal's Capital City. To secure access to the decoder, Ezra Bridger infiltrated the Academy for Young Imperials beneath the complex, adopting the guise of an Imperial cadet named "Dev Morgan". While Hera Syndulla and Kanan Jarrus remained aboard the Ghost in space, the remaining crew members, Sabine Wren, Garazeb Orrelios, and Chopper, waited outside the Academy to extract Ezra upon obtaining the decoder.
The Spectres' mission faced complications due to Imperial cadet Zare Leonis' pursuit to locate his sister Dhara, who had mysteriously vanished the preceding year while undergoing training as a cadet at the academy. Disenchanted with the Empire's policies concerning Lothal, Leonis infiltrated the Academy with the intention of locating his sister and actively undermining the Empire from within. Leonis received support from his girlfriend Merei Spanjaf, who had successfully gained access to the Imperial data network on Lothal by fabricating a fraudulent ISB account and employing snoopers to hack into the Transportation Ministry's headquarters.
For a duration of several weeks, Ezra Bridger underwent training at the Academy for Young Imperials under the alias "Dev Morgan." He was assigned to Unit Aurek, which formed a component of squad LRC077. Throughout his time undercover, Ezra established friendships with cadets Leonis and Jai Kell. Following the three cadets' achievement of first place in a demanding training evaluation within the Well, Commandant Cumberlayne Aresko rewarded them by granting them the "honor" of serving as aides at Imperial Headquarters situated upstairs. Having successfully completed the test, Ezra signaled to a disguised Chopper, who relayed the message to the other rebels. Unbeknownst to Ezra, Zare observed him signaling the droid.
Enacting his strategy, Ezra managed to slip into Agent Kallus' office under the pretext of delivering datapads. Ezra extracted the ZX-5 decoder from a computer positioned on the desk and concealed it within his cadet helmet. Upon opening the door to exit, he encountered Leonis, who pushed him back inside the office and spotted the decoder in his helmet. However, instead of reporting "Morgan," Zare cautioned him that removing the decoder from Kallus' office would trigger a sensor, initiating a facility lockdown. This unanticipated development postponed the Spectres' plans to intercept the Imperial convoy by a single day.
In private, Zare and Morgan engaged in a discussion regarding their motivations for resisting the Empire. After Morgan disclosed his involvement in a rebel cell, Leonis recounted the suspicious disappearance of his sister Dhara. Subsequently, the two cadets reached an agreement to secure a position within the top three the following day to regain access to Imperial headquarters. After Dev explained that his rebel comrades needed the decoder to intercept an Imperial shipment the following day, Zare revealed that his girlfriend Merei also needed the decoder to access some Imperial files on Dhara. After tossing a chance cube, Leonis and Dev reached an agreement that Morgan and his rebels would get to use the decoder first.
The following day, Zare and Dev executed their plans. Despite opposition from an obnoxious cadet named Nazhros Oleg, Ezra and Zare managed to secure positions within the top three. However, in the process, Dev was compelled to push Jai onto a lower repulsorlift platform, as Zare had been lagging behind in the assessment. Dev expressed regret for harming Jai but acknowledged that his mission held greater significance. Together, the two rebellious cadets proceeded to Imperial headquarters. Prior to the second attempt, Leonis had coordinated with Merei to generate a fictitious procurement order for spare podracer parts to divert Agent Kallus' attention.
Given that transporting the decoder through the door of Kallus' office would activate the sensor, Ezra entered Imperial Minister Maketh Tua's office to ascend into a ventilation shaft that extended over Kallus' office. While Leonis distracted Kallus with the fabricated order, the young Jedi utilized the Force to levitate the decoder into his palm. Kallus, already suspicious of the fake order, noticed Zare's distraction as he watched "Morgan" levitate the decoder. Upon turning around, however, Ezra had already seized the device and secured the grate to the ventilation shaft. En route back, Ezra overheard a conversation between Commandant Aresko and the Grand Inquisitor, whom he had encountered previously on Stygeon Prime. Aresko had identified two cadets who met the Inquisitor's "special criteria": Dev Morgan and Jai Kell. The Inquisitor announced his intention to arrive the following day to assess the cadets and apprehend them if they exhibited Force-sensitive traits.
After stealing the decoder, Dev informed Zare about his newfound predicament involving the Grand Inquisitor. When pressed by Leonis, Dev admitted to being a Jedi but refrained from disclosing his true identity. Ezra then passed the decoder to Chopper, who delivered it to Sabine and Zeb. Communicating via hologram, Ezra conveyed to his rebel comrades that he had to remain behind to prevent the Grand Inquisitor from abducting Kell. Sabine then contacted Hera and Kanan, who proceeded to the Imperial convoy's coordinates. While Kanan expressed concern over Ezra's decision to remain behind, Hera reiterated the importance of prioritizing their mission. Having completed their use of the decoder, the Spectres then passed it to Merei, who encountered them in the streets of Capital City.
Later that night, Dev awakened Jai Kell from his bunk and led him to a nearby storeroom where Zare Leonis was waiting. Due to the "betrayal" earlier that day, Jai initially did not believe them and thought it was a trick to get him expelled from the Imperial Academy. While Kell was skeptical of the Grand Inquisitor's existence, he believed that the Inquisitor could train him and give him a top rank in the Empire. Leonis was able to sway Kell over to their side by recounting his sister Dhara's disappearance. Since Kell's only family was his mother, he was unwilling to leave her forever.
Having won over Kell, Dev and Zare then put into a motion a plan which involved winning the next assessment in order to get a ride on an Imperial AT-DP walker. The following day, their escape plot encountered another unexpected problem. While Jai and Zare came in the top three, the second place was taken by Nazhros Oleg, who was unaware of their escape plan. Despite the predicament, Morgan told the other rebels to stick with their original plan while he found a way to get aboard the walker. Meanwhile, Chopper planted a bomb on one of the legs of another AT-DP walker.
Once aboard the AT-DP walker, Kell and Leonis put their plans into action. After hearing an explosion within the Academy's hangar bay, Jai used a blaster to stun the Imperial combat driver. Oleg then asked what Jai was doing. In response, Jai stunned him. Zare then took control of the walker and headed towards the Academy's blast doors. When Grint realized that the cadets' AT-DP had been hijacked, Aresko ordered that the Academy's blast door be shut. Using the walker's laser cannons, Zare managed to damage an approaching AT-DP outside the Academy, causing it to block the blast door. However, the walker then came under fire from an Imperial Troop Transport approaching from the plaza.
At that point, Ezra used his Force abilities to climb aboard the AT-DP; leading Aresko to believe that he was trying to stop the hijackers. At that point, the hijacked walker was struck down by the Imperial Troop Transport's laser cannons, causing it to topple to the ground. The walker's head landed outside the Academy. Ezra survived the fall, but found himself surrounded by several stormtroopers. However, Zeb and Sabine shot the Imperial troops. They then managed to evacuate Ezra and Jai on a landspeeder. However, Leonis chose to stay behind in order to find his sister. With Aresko, Grint, and more stormtroopers approaching the vicinity, Leonis pretended to fire upon his rebel friends in order to maintain his cover.
Meanwhile in deep space, the Ghost approached the Imperial convoy. The convoy consisted of three Imperial Gozanti-class cruisers, which each carried several TIE fighter escorts. Using the Force, Kanan sensed that the kyber crystal was aboard the middle ship. Kanan then used the Ghost's auxiliary ship, the Phantom, to lure the TIEs away from the convoy while Hera attacked the middle ship.
With the convoy under attack, the middle ship's Imperial captain ordered his crew to prepare the ship for a hyperspace jump while every remaining ship covered them. Braving enemy fire, Hera used the Ghost's firepower to strike the cruiser's engine systems, triggering a massive explosion, fueled by the kyber crystal, that destroyed the convoy ships and remaining TIE fighters. Before the explosion caught up with them, Kanan managed to dock the Phantom with the Ghost. The rebels then jumped into the safety of hyperspace.
The mission to destroy the kyber crystal gave the Spectres another victory against the Galactic Empire. It also had significant repercussions for Jai Kell, Zare Leonis, Merei Spanjaf, Commandant Aresko, and Taskmaster Grint. The Spectres managed to reunite in Lothal's wilderness. There, Hera arranged for Jai Kell and his mother to go into hiding. Despite his annoyance with Chopper and Zeb's body odor, Ezra came to appreciate his place in the Spectres as a result of the undercover mission at the Academy. In return, Kanan came to understand that Ezra was perfectly capable of looking after himself.
Meanwhile, Zare Leonis received praise from his Imperial Academy instructors and peers for trying to stop the "traitors" Jai Kell and Dev Morgan. He was later even awarded a commendation by Commandant Aresko. Later, Leonis was summoned for a private meeting with the Grand Inquisitor, who recognized Morgan as Ezra, one of the rebels he had encountered on Stygeon Prime. After confirming that Morgan was indeed a pseudonym, Leonis tried to probe into his sister Dhara's fate by claiming that he had a Force-bond with his sister.
Using the stolen decoder, Merei Spanjaf discovered that Dhara had been identified as Force-sensitive by the Grand Inquisitor and forcibly inducted into Project Harvester, a top-secret program run out of the Arkanis Academy. Merei's efforts to slice into the Imperial data network attracted an Imperial investigation which subsequently forced her and her family to go into hiding on the planet Garel.
Due to the rebel attack, the Lothal Academy's reputation was damaged and the Imperial authorities began screening all Imperial cadets for disloyalty. This incident was one of the many rebel activities on Lothal that preceded a planetwide crackdown on sedition. Later, Leonis was transferred to the Arkanis Academy under the pretext of rewarding him for his leadership abilities and loyalty. However, the Grand Inquisitor had arranged for this transfer in order to investigate his links to the Spectres. Before Leonis could find his sister Dhara, he was identified as a traitor and scheduled for execution. Due to the intervention of the Spectres and Merei, Zare and his sister were able to escape with their family into hiding on Garel.
Following a string of repeated failures to stop the Spectres, Commandant Aresko and Taskmaster Grint were executed by the Grand Inquisitor under the orders of Grand Moff Wilhuff Tarkin, the Governor of the Outer Rim Territories. Tarkin wanted to send a warning to his Imperial subordinates that the Empire would no longer tolerate any more failure.
Four years later, Ezra, Sabine, and Chopper wound up on a mission with notorious extremist Saw Gerrera, where they discovered the Empire was transporting another giant kyber crystal. This one was destroyed as well, when Gerrera rigged it up to the hyperdrive of the freighter it was being transported on, creating a bomb. After the mission, Kanan was reminded of the earlier incident, and he and Sabine wondered what the Empire could want with the crystals, and if it really was trying to weaponize them.
The Spectres' mission to destroy an Imperial kyber crystal shipment forms the main plot element of the Star Wars Rebels episode "Breaking Ranks," which premiered on Disney XD on October 27, 2014. The mission was also further expanded in Jason Fry's 2015 junior novel Servants of the Empire: Rebel in the Ranks, which was told from the point-of-view of Zare Leonis, a secondary character who first appeared in Breaking Ranks.