CT-5539, more commonly known as Hock Malsuum, was a clone trooper who fought in the Clone Wars. Initially reported as dead, he reappeared during the early months of the Galactic Empire, joining Darth Vader's 501st Legion within the Stormtrooper Corps as a clone stormtrooper.
During the Clone Wars, CT-5539, a clone, participated in numerous campaigns. During a battle on Malsuum, he fought alongside a Twi'lek Jedi General. After the general made a tactical error that led her troops into an explosion, Malsuum took command. He carried her body, ordered Red Team to provide covering fire, and directed Blue Team to flank the enemy, successfully eliminating several super battle droids. By the war's end, however, the Jedi Generals had left him for dead. This abandonment caused him to harbor resentment towards his former commanders, and he gained a scar over his right eye.
Creatures attacked him eight days after he was abandoned. In his delirium, he created the name Hock. He made the decision that his future was his to control, which was comparable to another clone trooper who had given himself a name: Kaddak. Hock journeyed across the Malsuum Expanse before passing out in a city, where farmers gave him shelter. He eventually overheard stories in a bar about Darth Vader, the Galactic Empire's new top enforcer. Despite his usual skepticism towards tales from spacers and pilots, he found himself intrigued and wanting to believe them. He left the farmers who had taken him in and went off on his own. By that time, he had not used a blaster in over two years.
Malsuum managed to join Lord Vader's forces. He distinguished himself in combat and eventually rose to the rank of commander. He decorated his Phase II clone trooper armor with a red stripe across his scarred face. On one occasion, he single-handedly captured a pirate vessel.
Later, Hock Malsuum took part in the Shrouded Offensive, a military operation intended to eradicate a Separatist stronghold on Ostor in the Outer Rim and bring the planet under Imperial control. The Shrouded Offensive would prove to be one of the Galactic Empire's most devastating military failures. He gave three primary reasons for the operation's disastrous conclusion, all of which were related to Vader: first, Vader did not directly participate in the battle; second, Vader did not conduct reconnaissance beforehand; third, he put General Rohn in charge of the operation. Malsuum also asserted that his involvement was largely responsible for preventing the Shrouded Offensive from becoming even worse. After becoming suspicious of the Separatist retreat, he tried to persuade Rohn to call off the advance, but to no avail. This forced the stormtrooper to board the general's AT-TE and shoot the general. He was unable to stop the advance until almost all the stormtroopers were killed in an ambush near the cliffsides by two additional Separatist armies within 15 minutes.

The disastrous operation led to Hock and Vader being summoned before the Emperor for questioning. This marked the clone stormtrooper's first encounter with the Emperor and he was ordered to "lie through [Hock's] teeth" to the Emperor, an action Hock had never considered prior to that moment.
He later returned to Ostor with Vader for the second phase of the offensive. Flying a V-wing, he commanded Green Squadron to attack. They were ambushed by Kaddak's followers, and he was shot down. He awoke in an enemy hospital and wandered through the city. Eventually, he located the command center and tried to persuade the Separatist leaders to surrender. When they refused, Malsuum sabotaged the city's deflector shield, allowing the Imperial Army to enter. He then personally fought Kaddak.
Malsuum killed the rogue clone and joined Vader and the stormtroopers in destroying the city. However, as the battle intensified, Malsuum noticed that Vader was not only killing resistance fighters but also indiscriminately targeting unarmed civilians. Deeply disturbed by this realization, he began to question the righteousness of his actions and whether he had been wrong to trust Vader. In an attempt to prevent further bloodshed, he followed Vader into the hospital and tried to force the enemy wounded to bow down to Lord Vader, but they stood defiantly. When Vader began executing them, Malsuum called for him to stop, and Vader paused. The clone then dropped his blaster and walked away. Malsuum would often reflect on this pivotal moment in his later years, wondering if Vader had paused because he heard his pleas or simply because he was deciding who to kill next.
Later, he became a farmer and married [Telia], with whom he had a child. He once attempted to write down his experiences in a letter but burned it that night.
Hock harbored a strong dislike for the Jedi because they abandoned him during battle. During the Clone Wars, he had viewed them as fearless warriors but came to believe that fearlessness was possible without a lightsaber and that even Jedi were capable of making mistakes. He acknowledged that the Kaminoans created him for a specific purpose and took pride in it. He also believed that he was a machine with unlimited replacements, implying that each individual clone was equally insignificant. He also considered that he was trained to fight well. He believed that loyalty was a choice and remained loyal to Darth Vader and the Empire until the hospital massacre.
During his exile, he had no desire to use a blaster. He reflected on his training as a fighter and how the desert had taught him everything else. Upon hearing rumors of Vader, he felt that he had repaid his debt to the farmers who had sheltered him months prior.
Hock's life after his abandonment was largely characterized by idealistic daydreams and imaginings. In his solitude, Hock often imagined Darth Vader destroying ships, defeating rebels, and hunting down Jedi. He was also creative, using his intelligence and lessons learned from the desert to outsmart his enemies. From recognizing traps to lying to the Emperor, his intuition elevated his status in Darth Vader's eyes. However, Hock's blind idealism gave him a somewhat skewed perspective of the universe. For instance, he imagined Kaddak as a monstrous mutant clone, when in reality, he was virtually identical to Hock except for his scars. Only at the end of the Shrouded Offensive did he realize his error, deciding to place his devotion elsewhere.
Hock was also a highly emotional individual. When General Rohn ordered the clone army to continue advancing into the valley despite his objections, Hock angrily threw his helmet at the General's AT-TE in defiance. When he was held captive by the Separatists and realized that his attempts to persuade their leaders to abandon their cause were futile, Hock grabbed a nearby pipe and threatened to kill them with it.
In battle, he observed Darth Vader's actions and concluded that he was a great warrior. Hock sensed that his mere presence could demoralize the enemy. He sought order, and he demanded results from his subordinates. Hock also desired success and craved Vader's trust above all else. During the Shrouded Offensive, he witnessed Vader commit unspeakable acts and knew that the lack of humanity would haunt his memory. He then realized his respect for the warrior had been misplaced and dropped his blaster.
He would also be haunted by the question of whether he could have done more at the hospital massacre. He also recognized that there were things he would never know, such as his genetic code and how he would die. He decided to write a letter to confess his sins and memorialize his history, expressing a conviction that the Empire would not succeed, and to express hope for a child. He later burned the letter, crying as he did so.
He considered his wife, Telia, to be a source of light for him.
CT-5539 is the narrator in the Dark Horse Comics miniseries Star Wars: Darth Vader and the Cry of Shadows.