THX-1138 was a clone of the bounty hunter Jango Fett. He went on and served under the 501 Legion and played part in many of the major battles. During a Jedi assault on Hypori is when Darth Vader, THX-1138, an Imperial officer, and three other troopers led an assault to kill all twelve Jedi. After Vader killed the first one, THX-1138 picked up the fallen lightsaber and killed two Jedi. Vader kept this a secret by slaying all of his men present. All but two of the twelve Jedi were killed, but Vader took THX-1138 as his apprentice after the failure with Galen Marek.