The HK-24 series assassin droid represented a specific model of assassin droid. These droids were manufactured by the Czerka Corporation during the Mandalorian Wars period. Recognizable by their characteristic red durasteel armor and significant level of independence, the HK-24s were engineered to mimic the appearance of protocol droids. This disguise allowed them to blend in and more easily execute their assigned targets. Although the HK-24 was considered a notable advancement in droid technology for its time, and was produced in large quantities by Czerka preceding the Mandalorian Wars, its lack of widespread consumer demand as an assassin droid led to substantial financial losses for the company. However, Czerka managed to recover a portion of these losses when Adascorp CEO Arkoh Adasca purchased the entire remaining stock of unsold HK-24 units in 3963 BBY. Adasca intended to utilize these droids in his search for the escaped Arkanian Offshoot scientist Gorman Vandrayk. Adasca deployed numerous HK-24s as security personnel on his flagship, the Arkanian Legacy, but all of them were ultimately destroyed when Vandrayk unleashed a horde of enormous exogorth creatures upon the Arkanian's ship. Some HK-24s, acquired by planetary governments prior to Adasca's bulk purchase, met their end through destruction or imprisonment after the Galactic Republic outlawed the model.
The HK-24, a type of assassin droid created by the Czerka Corporation, stood as a particularly lethal innovation in droid technology during the Mandalorian Wars era. Despite having red durasteel plating for armor and menacing orange visual sensors, the HK-24s were designed to appear as ordinary service droids to the casual eye, a deliberate design choice by Czerka. The HK-24s were, in reality, built to mimic protocol droids, allowing them to gain the trust of their targets and make the eventual kill easier. Although their appearance was unassuming, these droids were skilled with a blaster rifle and possessed considerable cunning, equipped with a heuristic processor to enhance their learning and reasoning abilities, as well as a translator unit enabling them to comprehend countless communication methods.
For close-quarters combat, the HK-24s could utilize a utility vibroblade, which helped the assassin droids specialize in dismemberment, or cutting off limbs. The HK-24s were capable of functioning effectively not only as assassins, but also as bounty hunters, although their use was criticized by organic hunters during the Mandalorian Wars. HK-24s were also employed for security purposes; their durasteel frames were quite resilient, able to endure powerful blows from larger adversaries, such as bulk-loading droids, with minimal damage. However, the HK-24s were not always reliable in cooperative situations. These droids were fiercely independent and harbored resentment towards other units of their class, each considering itself superior to its "redundant" and "artifact" counterparts. Placing multiple HK-24s together often resulted in them arguing and trading insults.
The HK-24 represented Czerka Corporation's first significant success in assassin droid production. It was mass-produced with the expectation of high demand from the Galactic Republic and various planetary governments leading up to the Mandalorian Wars between the Republic and the Mandalorian Neo-Crusaders. Czerka marketed the droids to planetary governments as a defense mechanism against the looming threat of the Neo-Crusaders, and achieved some sales. However, Czerka overestimated the market. Most individuals in the galaxy did not require an assassin droid for their daily lives, which resulted in the HK-24 becoming a financial failure. Production facilities were eventually closed and abandoned. Despite its failure for Czerka, the droids found significant use under Arkoh Adasca, the CEO of Adascorp, the galaxy's largest bioengineering firm. With the war approaching, Adasca planned to transform his corporation into a major galactic player by selling the destructive capabilities of the massive species of space slugs known as exogorths to one of the warring factions, effectively determining the outcome of the conflict. However, this plan hinged on the knowledge of a specific Arkanian Offshoot scientist, Gorman Vandrayk, who had left Adascorp over thirty years prior upon discovering the company's intentions to weaponize the creatures.
After an extensive search, Adasca's Rodian assistant, Eejee Vamm, discovered in 3963 BBY that Vandrayk was alive and had resurfaced after being spotted in security footage from the banking world of Telerath. In response, Adasca purchased the entire remaining stock of HK-24s and dispatched them to nearby systems to locate Vandrayk. Shortly thereafter, an HK-24 unit located the elusive scientist on the remote world of Ralltiir, managing to infiltrate his junk hauler, The Last Resort, by hiding in a crate of hyperdrive components. The HK-24 emerged from its hiding place after the ship entered hyperspace, quickly identifying a surprised Vandrayk, along with his close friend and protector, Jarael. Needing Vandrayk alive, the HK-24 considered the other Offshoot insignificant to his mission and decided to eliminate her. Jarael intervened to protect Vandrayk, and as the HK-24 approached—intending to attack the Offshoot with its vibroblade—the assassin droid was attacked and sent flying across the cargo hold by Vandrayk's massive bulk-loading droid, T1-LB. The HK-24 recovered, drew its blaster rifle and incapacitated the droid with a series of laser blasts, only for Jarael to attack it from behind with a chain. Jarael managed to damage one of the HK-24's sensors, but the droid gained the upper hand until it was destroyed in a surprise attack from behind by the Mandalorian warrior Rohlan Dyre, an acquaintance of Vandrayk and Jarael's who had secretly stowed away on their ship.
However, Vandrayk was soon compelled to return to Arkania due to illness, where Adasca manipulated Jarael into helping locate the Offshoot scientist. Vandrayk was quickly restored to health aboard Adasca's flagship, the Arkanian Legacy, where he was forced to resume work on the exogorths—under Adasca's orders, he was constantly accompanied by a squad of HK-24 units to ensure compliance. Once the Arkanian Legacy arrived at Omonoth, the location of a large number of dormant exogorths, the time for the auction had come. Invited parties from the Republic Navy, Mandalorians, and the Jedi Order's interventionist Revanchist faction gathered on the Adascorp flagship, and Adasca began openly deploying his HK-24 units as security. Adasca also directed several HK-24s to secure the ship's brig after capturing two high-profile prisoners: Zayne Carrick, the alleged perpetrator of the Padawan Massacre of Taris, who arrived in the custody of the Republic delegation, and Lucien Draay, a Jedi Master who had been poisoned and incapacitated by Adasca after he unexpectedly crashed the auction.
Guarded by five HK-24 units, Carrick and Draay managed to overpower their captors and escape. They then devised a plan with Republic Lieutenant Carth Onasi to disrupt the auction and thwart Adasca's power grab. With Carrick disguised as a Mandalorian, the prisoners and Onasi created a distraction allowing Draay to attack and eliminate Draay's personal guard of HK-24s. Meanwhile, Vandrayk reprogrammed the HK-24 guarding him to destroy the exogorth command station as he escaped, and directed the massive beasts to tear the Arkanian Legacy apart. Adasca still had several dozen HK-24 units defending him to the end, but they were all destroyed along with their master when the exogorths obliterated the ship and ended his dreams of domination. Despite this, HK-24 units continued to see action during the Mandalorian Wars. Those not purchased by Adasca fought against the Mandalorians, as Czerka had promised. The droids proved highly effective, killing numerous Mandalorians and destroying hundreds of Basilisk war droids.
Sometime after the Mandalorian Wars, the HK-24 model was declared illegal and became rare throughout the galaxy. HK-24 units were either destroyed or imprisoned. One particular unit was found harassing civilians on the planet Nouane/Legends and was subsequently confined to a cell on the prison planet known as Belsavis. Rumors of its imprisonment spread, but remained unconfirmed. Several years after the war, during the Jedi Civil War, the Dark Lord of the Sith Darth Revan based his design for the HK-47 assassin droid on the HK-24, incorporating several of his own enhancements. The HK-47, in turn, became the foundation for the HK-50 assassin droid, which was mass-produced by Revan's Sith Empire during the war.
By the Third Galactic War, very few HK-24 units were known to remain. Due to the presence of Basilisk war droid schematics in its memory core, the Alliance Commander, with assistance from a droid collector known as the Curator, located the HK-24 unit imprisoned on Belsavis to aid Lane Vizla in repairing a Basilisk war droid that had been subjected to experimentation by Kur Ha'rangir. After retrieving the core, the chassis was recovered by retrieval experts working for the Curator. The Commander and Vizla installed the core into an astromech droid, but the HK-24 astromech became highly agitated and attempted to self-destruct, only to fail due to the absence of such a mechanism in its new body. Noticing the small Basilisk droid that the two intended to repair, it attempted to follow its last directive and destroy the droid, forcing Vizla to intervene.
The Commander returned to the Curator, who expressed some surprise at the choice of an astromech droid as a chassis, but still agreed to help create a restraining bolt to ensure compliance. To modify and access the HK unit's heuristic processor, the Curator reinstalled the memory core into its original chassis. Unbeknownst to him, the droid was equipped with a reserve power supply and activated immediately. Believing it had a mission to kill the Zabrak collector, the droid pursued him into his panic room. The Commander ultimately subdued the droid, and the memory core was removed and reinstalled into the astromech, now equipped with a restraining bolt. Now under control, Lane and the Commander were able to interrogate it for the schematics of the war droids, though the astromech continually argued with itself over its actions. Lane decided to name the droid "Shebs," meaning "backside" in Mando'a, to reflect its troublesome nature.
The initial appearance of the HK-24 assassin droid occurred in Knights of the Old Republic 13, an issue of the Star Wars: Knights of the Old Republic comic book series. The issue was written by John Jackson Miller and published in 2007. Following the droid's second appearance in the series' next issue, Miller revealed that the HK-24's designation was inspired by NASCAR driver Jeff Gordon. Gordon, sponsored by Lucasfilm, drove a #24 car featuring an image of Yoda to victory in the 2005 Aaron's 499. Miller kept a miniature model of Gordon's Yoda car on his writing desk. The HK-24 droid subsequently appeared in the story arcs Nights of Anger and Daze of Hate, with illustrations by Brian Ching, Harvey Tolibao, and Bong Dazo throughout its appearances in the series.