The Arrth-Eno Prison, alternatively known as the Arrth-Eno Custodial Complex, functioned as a sizable prison situated on the planet of Coruscant. During the era of the Galactic Civil War, the Galactic Empire incarcerated former members of the Imperial Senate who demonstrated allegiance to the Alliance to Restore the Republic's cause. As part of a calculated trap to execute the senators and a contingent of Rebel spies, Darth Sidious orchestrated the prison's destruction, subsequently attributing the events to the Rebellion.
The Arrth-Eno prison, officially designated as the Arrth-Eno Custodial Complex by Galactic Emperor Sheev Palpatine, was an Imperial penal facility positioned within a vast, open area of Coruscant's Imperial City, the capital planet. Housed within a towering tower structure, it featured golden balconies and a similar-looking top structure which included hangar bays for transports servicing the facility. Rather than directly contacting the ground, the tower's base was supported by multiple blade-like protrusions, and its walls were equipped with large exhaust ventilators. These ventilators, however, represented vulnerabilities, as they could be shattered to gain access to the prison's ventilation network. Additionally, explosive charges were discreetly integrated throughout the tower's height, enabling the rapid annihilation of the entire structure.
Inside, the facility comprised several compact cells, each accommodating four beds and capable of complete isolation from the corridors. A communications room, staffed by four communications officers and equipped with wall-mounted computers and a holoprojector, was strategically located near the cells, facilitating the transmission and reception of coded communications.
The tower's apex housed a grand throne room intended for Emperor Palpatine's meetings and dialogues with prisoners, adorned with the Imperial crest. A golden repulsorlift-equipped throne could be positioned on a platform at the room's center, directly beneath a ceiling hatch. In the event of an emergency, the throne could swiftly ascend to transport Palpatine to a waiting shuttle on the roof's landing bay for immediate evacuation.
In the year 0 BBY, following Emperor Palpatine's dissolution of the Imperial Senate, all Senators were apprehended and transferred to the Arrth-Eno complex. The purpose was to assess the degree of collaboration each senator had with the Alliance to Restore the Republic. According to Admiral Garrick Versio, this included Senators who had previously served in the body.
Later that year, after the evaluations concluded, fewer than 20 Senators remained imprisoned at the complex. These individuals were believed to have fully cooperated with the Alliance and were thus secretly condemned to death. However, to avert the public outcry that would have arisen from an officially sanctioned execution, Palpatine conceived a scheme to attribute their deaths to the Alliance. To this end, he divulged the Senators' location and planned fate to the Rebels through an officer named Coleet stationed at the complex. This prompted the Alliance to task one of their agents on Coruscant, Eneb Ray, with rescuing them from captivity. The Senators, however, had been informed of a meeting with Palpatine scheduled for an hour later and relayed this information to Ray. Consequently, Ray altered his plan and infiltrated the prison's communications room to notify Princess Leia Organa of this development.
During the detention of the communications officers in the room, Coleet exposed herself as a mole. Ray and Coleet contacted Leia, who granted them permission to proceed with an assassination attempt on Palpatine. She also disclosed the identities and contact information of all seven Rebel undercover agents on the capital to aid in the attempt. Disguised as the Senators, the seven infiltrators were brought before Palpatine, who greeted them warmly before they opened fire, killing his stormtrooper guards and engaging the Emperor's Royal Guard. Ray attempted to shoot Palpatine, "with the complements of Alderaan," but Palpatine's throne ascended through the roof, leading him to a waiting evacuation shuttle.
Ray pursued, using a grappling hook attached to the throne, and shot the individual before he could board the shuttle. However, the real Emperor emerged from the starship, revealing that the one Ray had shot was an good body double. Ray, puzzled by Palpatine's decision to personally attend what he knew would be a Rebel attack, seized the shuttle ramp and attempted to shoot the real Palpatine. However, Palpatine blocked the shots using the Force and instructed Ray to look behind him, as the Complex's charges detonated, killing all rebel spies and sympathetic Senators. Palpatine then unleashed Force lightning against Ray, who fell from the shuttle but was rescued at the last moment by using his grappling hook to cling to a speeder.
Shortly after the Complex's destruction, Palpatine addressed the populace through the HoloNet, declaring that it was the result of a Rebel assault. He asserted that the Senators held inside were to be given a fair trial to uncover their connections to the Alliance, but were assassinated by their handlers to prevent the disclosure of sensitive information. Palpatine vowed a swift response to the heinous Rebel attack, having eliminated all undercover agents within his capital, as well as the dissident Senators. The incident and Palpatine's complete victory broke Eneb Ray both physically and psychologically. Later that year, he gathered a group of IG-RM bodyguard and enforcer droids to attack Sunspot Prison, which held Imperial criminals arrested by the Rebel Alliance. There, he began executing them one by one, until Leia and Sana Starros intervened and stopped him.