Captain Nelex was a male Human who served the Republic Expeditionary Forces during the era known as the Cold War.
In the year 3643 BBY, the last of the Cold War, Nelex received orders to collaborate with Jedi Master Cin Tykan and his Padawan, Aris Vauranelle, on the planet of Taris. This world had been ravaged three centuries prior by the Sith Lord known as Darth Malak. When Master Tykan ventured out on a research mission to gather pollution metrics and exhibited no indications of the rakghoul plague, Nelex attempted to communicate with him, but received no response. Enraged upon discovering that Tykan was responsible for the demise of numerous workers under his command, Nelex requested that the Jedi Knight tasked with retrieving Tykan to the base eliminate the Jedi Master. As Tykan launched an assault on the Republic base and kidnapped his Padawan, Nelex stood his ground, fighting off rakghouls alongside his troops, yet failed to prevent the Kaleesh Jedi from succeeding. Upon the Jedi Knight's return, bearing news that Tykan had been healed and was en route back to Tython for recovery, Nelex was incensed that the Jedi had prioritized the well-being of their own over delivering justice for the fallen.
Despite his role as a Republic soldier, Nelex was a strong proponent of capital punishment for crimes committed. He persistently urged the Jedi Knight to execute Tykan for his assault on the soldiers under his command, and he was filled with fury when the consular showed mercy to their fellow Jedi.