Due to his latent Force-sensitivity, Heezo was brought to Coruscant at a very young age to be trained as a Jedi. At some point, he failed the Jedi Trials and was transferred to by the Council of Reassignment where he worked as a droid maintenance technician.
In 33 BBY, Heezo was working in the Temple's surface fleet garage when the repulsorlift of a nearby transport malfunctioned while undergoing repairs led by Masters Saesee Tiin and Plo Koon. Koon used the Force to resolve the issue, but failed to keep a bucket of drained engine coolant from spilling over him. Heezo and the incoming Padawan Obi-Wan Kenobi both assisted Koon in cleaning up the mess.
Kenobi then requested a vehicle to help transfer some newly-arrived refugees from the spaceport to the migrant center, explaining that a funding issue was preventing the Republic from dealing with the matter and that his master, Qui-Gon Jinn, wished to expedite the matter with Jedi resources. Koon and Tiin pointed out that they were in no position to help with much of the Order's surface fleet grounded for an overhaul. However, Heezo offered to cash in the favor a hoverbus driver owed him in order to provide the transport needed. With Koon's approval and Kenobi's thanks, Heezo left the hangar and made the necessary arrangements.
Sometime later, Master Mace Windu visited the Temple's vehicle maintenance hangar while Heezo was assisting Tiin. Pausing for a moment as he moved half of an astromech droid over to a Jedi starfighter, Heezo commented to Windu that with all the Council members leaving Coruscant, that they must be going on a great adventure.
By 22 BBY, Heezo had been recruited by the Sith Lord Darth Sidious to spy on and influence members of the Jedi Order, with the ultimate goal of pushing them to one day become agents of the Sith. Heezo was especially fitted for this task: despite having left the Order, he retained a connection to the Force that allowed him to pick up on the darker emotions of individuals.
After the First Battle of Geonosis, he found a suitable candidate in the newly anointed Jedi Knight Iskat Akaris, who he casually began to interact with after she discovered the secret garden where he liked to do his droid repair work. The two had many conversations and developed a friendly relationship over the course of the Clone Wars, during which Iskat would confide in him feelings she could tell no one else, such as her frustrations with the Jedi Council and the Order as a whole.
Heezo encouraged these feelings of mistrust and anger, advising her to break the tenets of the Jedi Order, to follow her heart, and embrace her emotions and passions. Secretly, he reported all of Iskat's developments to Sidious, and, after the execution of Order 66, Heezo survived the siege of the Jedi Temple and began working for the Inquisitorius in a similar role to the one he had held at the Jedi Temple for over forty years.
Around 19 BBY, Heezo encountered Iskat again, who had fallen to the dark side and joined the Inquisitorius as the Thirteenth Sister. While exploring the Inquisitorius Headquarters on Coruscant, she discovered him at work in a hidden chamber. By this point, Iskat had learned of Heezo's role during a conversation with Sidious and considered him a traitor to her. Heezo meanwhile was happy to see her and was confused by her anger at his actions, insisting that she had greater freedom than she did before as a Jedi. Suspicious that he now reported to the Grand Inquisitor, she quickly cut him down with her lightsaber, reveling in her revenge.
Heezo was a Selonian whose eyes were colored brown and his fur chestnut-brown with beige stripes, later graying with age. He stood 2 meters tall. He was mild-mannered, eager to please and generally well-regarded throughout the Temple. However, he secretly harbored resentment against the Order for his failure to achieve Knighthood, leading to him to work as a proxy for the Sith Lord Darth Sidious. As a believer in individual autonomy, he empathized with Iskat Akaris' struggles, but also used them to manipulate her into turning against the Jedi. Heezo believed that he was doing Akaris a service by doing so.
A former Padawan, Heezo was unable to pass the Jedi Trials. However, he secretly maintained a strong talent for sensing the hidden emotions of others via the detection of pheromones, an ability native to his species, but enhanced in him by the Force. His aptitude for droid maintenance allowed him to remain at the Temple as a technician.