- "Manifesto: The maker created me for the sole function of deleting high-ranking organic troublemakers from the galaxy. These deletions must be conspicuous, and provide an object lesson to other organic troublemakers! All other mission parameters are secondary."
- "Schematics for HK generation 51: Blaster to accuracy ratio: increased by 21%. Durasteel impact frame resistance: increased. Conclusion: halting production. Units are in standby mode, pending further testing of behavior cores and assassination protocols."
- ―Log of the HK-51's development status
Despite the ban on HK-series assassin droids by the Galactic Republic, the Czerka Corporation started to develop and manufacture several HK-51s on Nar Shaddaa in secret during the late stages of the Great Galactic War. This order was for the reconstituted Sith Empire, who intended to deploy the new droids around a decade into the Cold War.
Lost and foundEdit
Sometime after 3668 BBY, the Sith warship Fatality, carrying the droid shipment, was hijacked by a Dread Masters' apprentice, who attempted to land and deploy them upon the planet Belsavis to in a bid to rescue his captured masters. The Republic's unit stationed on the planet shot down the vessel, which crashed and sank into the frozen waters of Section X. Not only was the only known shipment of HK-51 units lost, but slicers of unknown affiliation managed to delete all schematics of HK-51's design from Czerka's network. The only known remaining copy rested on board the disappeared Czerka research ship called the Theoretika, which lost connection with Czerka's network, saving it from the slicer's attack. The Fatality and its lethal cargo remained hidden until around 3640 BBY, when the escaped Dread Masters finally located their stolen cargo. 
Upon its rediscovery, the Dread Masters swiftly secured the site. They fought off severe attacks from both Republic and Imperial forces, causing major causalities for both sides. The Dread Masters managed to hold onto the wreck, attempting to access its cargo-hold containing the HK-51s, until an unknown spacer fought their way through the Dread Masters forces.
The spacer managed to enter the cargo-hold, but was disappointed to find that almost all HK-51s aboard were beyond repair after the crash and years of exposure to the frozen environment. Only a single HK-51 was salvageable, but even he needed several critical parts replaced. Unfortunately, due to the loss of the HK-51 schematics, not even Czerka had the parts required. Undeterred, the spacer left to locate the wreck of the Theoretika and the last copy of the lost schematics.
Galactic scavenger huntEdit
Arriving on the Theoretika, discerning what had happened to the wreck, and defeating the monstrous experiments on board, the spacer found and downloaded the HK-51 schematics. After departing the wreck, the spacer began their search for the parts HK-51 required. Their search led them to the Outlaw's Den on Tatooine. There the spacer found a Jawa who sold them a wrapped HK transistor, as well as a Burba Seismic Excavator/Scanner, which would help locate the remaining parts. The spacer searched the Sinking City of Taris and the Glacial Fissure of Hoth, and even enlisted help to search the Dark Temple of Dromund Kaas and the Jedi Temple of Coruscant. Even still, more parts were required. The loyalty chip was recovered from the legendary Force user Revan upon the spacer encountering the ancient Jedi. Lastly, the necessary Weapons Protocol software could only be found in the memory banks of the infamous assassin droid HK-47, who had been found, repaired, and upgraded by the newly proclaimed Emperor Malgus. Defeating the ancient droid and recovering the last component needed, the spacer returned to the wreck of the Fatality.
Once again fighting their way through the Dread Master forces, the spacer reentered the Fatality. With the help of a droid engineer assigned to them, they repaired and reactivated the sole surviving HK-51. Upon activation, the droids drew his weapon and frightened off the engineer before cheerfully greeting the unknown spacer. The spacer recruited HK-51 to join them upon their adventures, the droid accepting the spacer as his new master.
An efficient and loyal companionEdit
While serving his new master, HK-51 started to become aware that his combat/assassination efficiency was swiftly declining. Analysis of the trend also showed that if this continued, then he would eventually be unable to function. The problem was discovered to be a failsafe subroutine buried deep within HK-51 programming. This failsafe would cause the eventual shutdown unless HK-51 successfully assassinated at least one individual on a implanted kill list, though killing anyone would slow the degradation of his protocols. His master dispatched HK-51 to assassinate one of these targets, a mission that HK-51 successfully completed. After the mission, HK-51 reported that his protocols were as efficient as the day he was manufactured. Coming to admire his master, almost to the level of idolization, HK-51 worried that one day he would be reprogrammed to turn on the master he so respected. Searching for a way to resolve this, HK-51 found a loyalty subroutine (most likely within HK-47's loyalty chip recovered from Revan) that would permanently set his loyalty to his master and anyone his master specified. Even if reprogrammed, this subroutine would prevent HK-51 from attacking the spacer. HK-51 was overjoyed and congratulated his master and suggested they celebrate by killing a large number of enemies.
- "Correction: I have never been to a place called Asylum, and have never met you before. If you choose to continue the insinuation that I am anything other than... "
"Ugh. Okay. Okay. Just don't call me a meatbag."
"Query: What is a meatbag?"
- ―HK-51 and Tora
By 3632 BBY, HK-51 was present on the Eternal Alliance's base on planet Odessen. The Outlander, HK's previous master, later appeared and organized the group into attacking the Eternal Empire. During a party at the Odessen Cantina, the droid was confronted by Tora, who mistook him for HK-55, a droid she just recently encountered with the Outlander on the Spaceport Asylum, despite HK-51's confused denial.
- "Encouragement: Veiled mockery is an inefficient means of expression. If I did not like you, master, you would be dead."
HK-51 was designed to be a lethally efficient assassin/bodyguard and to take great enjoyment and pride in his duty. Quite unlike his predecessors he was programmed to be very polite, cheerful and friendly to his master and his master's allies. His programmers felt that previous models were too unsettling in their brutality. HK-51 himself even referred to models like HK-47 as "unstable." HK-51 did not seem to express any sort of hatred or disgust with organic beings or other droids that was so common to previous HK models. HK-51 also expressed dislike of political backstabbing and faction infighting, though he would partake in both if ordered to by his master.
While he was capable of both precision assassinations and mass murders, he much preferred to assassinate singular targets who were difficult to hunt. In this way, he was much more like HK-47 than his direct predecessors, the HK-50s. Much like HK-47, HK-51 viewed his assassinations as an art form. Despite this, he was programmed to put efficiency ahead of art, though he most enjoyed it when he could have both.
Unique to him, he quite enjoyed organics, as his negotiation/protocol programming was more prominent than previous models. He himself proudly stated that he was an excellent conversationalist. HK-51 also frequently used code words so as not to give away his true nature and purpose around those who may be alarmed. He often referred his targets as "undesirables" or "troublemakers," assassination/murder as "liquidation" or "deletion," and those who would be alarmed if they discovered his true purpose as "polite company." HK-51 also often referred to a "Maker," which seemed to be some sort of deity responsible for fate.
- "Declaration: Troublemakers beware--the Maker's greatest assassin is coming for you all!."
HK-51 was the most advanced HK-series droid to date. He featured several improvements and upgrades over his predecessor models. Besides being more armored and accurate than previous models, HK-51 was far more mobile and maneuverable. He was capable of faster and more fluid motions, almost able to replicate those of organic humanoids, perform leaps, and perform combat rolls.
HK-51 also had built-in weapons and equipment: wrist-mounted micro-missile launchers and railgun, hidden smoke grenades, a stealth field generator, and the ability to repair himself if critically damaged. If all other options failed, HK-51 was implanted with a powerful explosive which he could activate in a kamikaze attack to complete his mission.
Beyond his combat abilities, the protocol functions of HK-51 were improved, including the addition of extensive and impeccable cooking protocols. This allowed him to better disguise himself as a protocol droid.
Behind the scenesEdit
- "Revelation: We have already begun construction on a new generation of HK units. When the last of our deficiencies are accounted for and corrected, they shall be the most formidable assassination droids in the galaxy."
- ―An HK-50 assassination droid
In a removed part of Star Wars: Knights of the Old Republic II: The Sith Lords, HK-47 would confront G0-T0 on Malachor V, and a group of HK-51 droids would come and help him defeat G0-T0, if HK-47 had programmed them to aid him while in the HK Manufacturing Plant. (HK-47 could also choose to destroy them, causing him to lose to G0-T0.) The HK Manufacturing Plant was also removed from the game.
HK-51 droids later made an appearance in the 2011 video game Star Wars: The Old Republic, as companion characters for players of all classes. At level 50, a small quest chain in the Section X area of Belsavis leads to the discovery of the crashed Imperial battlecruiser Fatality, carrying a full complement of damaged but salvagable HK-51s. To claim an HK-51 for themselves, the player must first team up with others to explore the abandoned Czerka Corporation cruiser Theoretika in the Unknown Regions, and obtain a set of HK schematics. Afterwards, they must collect certain HK parts from Coruscant, Dromund Kaas, Taris, Hoth and Tatooine, from the False Emperor flashpoint on normal or hard difficulty, and either the Maelstrom Prison (Republic) or the Foundry (Empire) on hard mode. The part on the capital worlds (Coruscant and Dromund Kaas) requires a character of the opposite faction (i.e. making a Republic character to obtain the part on Coruscant for an Imperial "main") of at least level 10, the level around which players normally leave their starter world. After the parts are collected, the player returns to the Fatality wreck on Belsavis, and confronts a Sith of the Dread Host called "The Lord of Agony," again with a group. After the Lord of Agony is defeated, the player may claim their HK-51.
HK-51 will argue with HK-47 if the player brings him along during the battle against HK-47 during the mission False Emperor. HK-51 claims that HK-47 is an inferior model, while HK-47 defends that he is still the pinnacle of HK models. 
- Star Wars: Knights of the Old Republic II: The Sith Lords (Cut content)
- HK-51 Revealed (First appearance)
- Star Wars: The Old Republic (First identified as HK-51 series assassin droid)
- Star Wars: The Old Republic: Rise of the Hutt Cartel
- Star Wars: The Old Republic: Galactic Starfighter
- Star Wars: The Old Republic: Galactic Strongholds
- Star Wars: The Old Republic: Shadow of Revan
- Star Wars: The Old Republic: Knights of the Fallen Empire (Mentioned only)
- Star Wars: The Old Republic: Knights of the Eternal Throne
Notes and referencesEdit
- ↑ Star Wars: The Old Republic: Codex: The Fatality Crash
- ↑ 3.0 3.1 3.2 3.3 Star Wars: The Old Republic, Mission: Fatal Errors (Empire)
- ↑ 4.0 4.1 4.2 4.3 Star Wars: The Old Republic, Mission: The Fatality (Republic)
- ↑ HK-51 companion dialogue
- ↑ Community Developer Blog: HK-51 Classified Intel
- ↑ Star Wars: The Old Republic: Codex: HK-51
- ↑ Star Wars: The Old Republic, Mission: False Emperor