Some time after the events of the Assault on Cymoon, a disastrous scheme known as the Arrth-Eno Mission unfolded. This operation, led by Rebel spy Eneb Ray, aimed to eliminate Emperor Palpatine, the supreme leader of the Galactic Empire; however, it ultimately failed. The mission's genesis lay in Ray's infiltration of the Arrth-Eno Prison Complex on Imperial Center, also known as Coruscant, with the initial goal of liberating a group of senators sympathetic to the Rebel cause who were slated for execution. During his infiltration, Ray discovered the Emperor himself was scheduled to be at the prison.
Six additional Rebel operatives situated on Coruscant, including Coleet, provided support to Ray. Together, they launched an assault on who they thought was the Emperor. However, the target was merely a body double, who perished. The entire scenario was a carefully orchestrated trap by the Emperor, designed to eliminate the Rebel spies present on Coruscant, execute the senators, and secure a propaganda victory against the Rebellion. The Emperor's scheme proved successful, resulting in the deaths of all the spies and senators, with the exception of Ray.
Following the theft of the Death Star plans, Emperor Palpatine took the step of dissolved the Imperial Senate, thereby eliminating the last vestiges of the Old Republic. In the aftermath of the Battle of Yavin, several former Imperial senators, including Nadea Tural, were apprehended for collaborating with the Alliance to Restore the Republic. These senators found themselves imprisoned within the Arrth-Eno Prison Complex, a heavily fortified tower structure. Palpatine had determined to execute all political prisoners at Arrth-Eno, a decision influenced by the Assault on Cymoon and other prior victories of the Alliance.
In the year 0 ABY, the Rebel Alliance maintained a network of seven spies in the galactic capital of Coruscant, including Eneb Ray, who operated under the guise of Imperial tax collector Tharius Demo. After gathering intelligence regarding shipping and procurement activities in the Core sectors, Princess Leia Organa tasked Ray with the mission of rescuing the senators who were facing execution. Organa provided Ray with essential resources, including maps, relevant access codes, and a starship prepared to smuggle them off-world.
Ray utilized a grappling hook to ascend the prison complex. He employed a grenade to create an opening in the ventilation system. After infiltrating the ventilation shaft, Ray ambushed and incapacitated a stormtrooper before reaching the prison cell where the senators were confined. Before Ray could extract the prisoners, Tural cautioned him about the Emperor's impending arrival to oversee their execution.
Forcing his way into the command center, Ray ambushed the prison guards and coerced them into releasing their holsters and blasters. Ray also encountered the rebel mole Coleet, who was disguised as a prison guard. While Ray communicated with Organa via hologram, Coleet activated the scrambler to prevent the Imperials from tracing her location. Ray informed Organa about the Emperor's planned visit to the prison and shared his intention to assassinate the Emperor.
Despite her reservations, Organa conceded to Ray's argument that they should not forgo the opportunity to eliminate the Emperor. She consented to commit the rebellion's six other agents on Coruscant to this audacious undertaking.
Approximately an hour later, the "Emperor" made his entrance on a repulsorlift throne, accompanied by several Royal Guards and stormtroopers. He commanded the captive senators to approach, only for them to reveal themselves as rebel agents. Ray and his fellow agents initiated gunfire on the Royal Guards and stormtroopers, resulting in casualties on both sides. Simultaneously, Coleet and the senators observed the skirmish via hologram and offered encouragement.
Eneb employed his grappling gun to dislodge the helmet of a Royal Guard, thereby incapacitating the individual. Before Ray could target the "Emperor" with gunfire, the target escaped on a repulsorlift platform to the landing platform above. Resolved to eliminate the "Emperor", Ray managed to hold on with his grappling gun. Upon reaching the landing platform, Eneb successfully shot the "Emperor" and two stormtroopers dead before they could board an approaching Lambda-class shuttle.
Eneb swiftly realized that the individual he had killed was a decoy. The real Emperor arrived on board the shuttle and mocked Ray. Still determined to complete his mission, Ray boarded the gangplank and fired at the Emperor. At that moment, the prison complex detonated, resulting in the deaths of all the senators, rebel agents, prison guards, and Imperial soldiers inside. The bombing had been orchestrated by the Emperor as a deliberate trap and propaganda maneuver.
With Ray distracted by the explosion, the Emperor assaulted him with Force lightning, causing him to plummet through Coruscant's skyscrapers. Ray managed to survive by using his grappling gun to latch onto a passing airspeeder.
Following the bombing of the Arrth-Eno prison complex, Palpatine addressed HoloNet and asserted that the rebels had detonated the prison in an attempt to prevent the senators from testifying about how they had been manipulated by the rebellion. The Emperor seized the opportunity to portray the tragedy as a terrorist attack and vowed retribution against the rebels.
Ray was profoundly affected by the failure of the mission and acknowledged that he had been outmaneuvered by the Emperor. With the mission in ruins, Ray met with Organa's rebel contact, who turned out to be the export merchant he had previously rescued. Subsequently, the two escaped off-world.
Convinced that the rebellion lacked the capacity to prevail in the Galactic Civil War, Ray embraced extremism and disappeared into hiding. Eneb's face also bore the scars of the Emperor's Force lightning. Driven by a desire for vengeance against the Empire, Eneb assembled a force of mercenaries and IG-RM bodyguard and enforcer droids to attack Sunspot Prison and eliminate Imperial prisoners held there. However, his efforts were thwarted by the combined efforts of Organa, the smuggler Sana Starros, and the rogue archaeologist Chelli Lona Aphra. Eneb was captured but later escaped from rebel custody. More than three decades after the failed rescue attempt, Leia Skywalker Organa Solo expressed her regret that she could not have saved the senators in the same way she led the Mission to rescue the survivors of Alderaan.
The Arrth-Eno Mission made its debut appearance in the Marvel Comics story Star Wars Annual (2015) 1, which was released on December 9, 2015. It was conceived by Kieron Gillen, with illustrations by Angel Unzueta, and colors by Paul Mounts. The narrative of the Arrth-Eno mission is presented from the perspective of Eneb Ray, the comic's central character.