Instead of killing him, however, Darth Vader used him, tortured him, and probed his mind for information concerning the whereabouts of Halagad's fellow Jedi. This information was used to hunt down and murder many other Jedi Knights, and the process left Halagad a broken man. Giving into fear and panic in the presence of Darth Vader and his brutality, the Dark Side eventually overtook Halagad and claimed his spirit as its own.
Even still, Ventor managed to steal an Imperial ship and flee from the clutches of the Sith Lord. Rather than pursue him however, Darth Vader knew that Halagad would soon be no more, and let him flee. A broken man, filled with guilt and his mind racked with pain, Ventor sped across the galaxy eventually coming to the remote world of Trinta, an ominous planet, also home to a Dark Side nexus. However, Ventor was not strong enough to turn away and embraced the Dark Side making Trinta his home.
There he lived for years in a genuine hell, haunted by the faces of those whose deaths he felt responsible. Nearly two decades later, a group of Alliance agents crash-landed on the planet and in the group was a Force-sensitive Rebel who sensed Halagad's presence on the planet. Making their way, following the feelings through the Force, they were assaulted by illusions of attacks by fierce creatures, Dark Jedi, and other images. Eventually they came upon an old a gnarled tree, the entrance to Halagad's cave and home.
Once inside, Halagad began a series of twelve tests, each designed to elicit anger and hatred from the Alliance troops; however, through their combined strength, they were able to resist and eventually confront Halagad who had become old, wizened, with little hair and a meek frame. Face to face, Halagad urged the Rebels to kill him so that they may take his place in the Dark Side nexus. Halagad's insistence was genuine however, as he really wished to die to be freed from the torment he had been living for the past twenty years.