Vetraas was already an old warrior when his commander, executor Zoranis, was killed in combat with aliens. Along with second-in-command Adun, Vetraas was chosen to wash, dress and sit with Zoranis' body before he was borne along the Road of Remembrance.
Adun was swiftly promoted to executor. Some time later, the Conclave's leader, Kortanul, called upon Adun to secretly meet them at their Great Forum alone. However, Adun brought Vetraas with him. Kortanul was displeased, and made both Vetraas and Adun enter deep into the Khala where he formed a deep mind-meld with Adun and Vetraas to ascertain their loyalty.
Kortanul told the two about a new threat to the protoss; rogue heretics who refused to embrace the Khala. He offered them a rogue prisoner, Raszagal, to question, so they could come to peace with the decision of the Conclave -- extermination of the Rogues.
Adun brought Raszagal with him to his Citadel so the other high-ranking Templar would understand the reasons behind the execution, but both he and Vetraas were convinced that Raszagal wished no harm. Kortanul demanded Adun execute Raszagal, quickly, however. Vetraas suggested that the other heretics might not be harmless, but the interrogations showed that these other rogues were also harmless. Nonetheless, Vetraas was never as enthusiastic about helping the rogues as Adun was.
Adun decided to fake the executions, as well as teaching the rogues how to hide from the Conclave. Vetraas disapproved, since he knew Adun was learning from the heretics as he taught them this technique, and he also worried about the speed at which the rogues learned. He had reason to worry; some of the rogues lost control of their powers, creating huge psionic storms which swept over parts of Aiur, killing protoss, animals and even destroying the jungle.
The Conclave quickly tracked the storms back to their source, only to discover several "executed rogues" had only recently died! Shocked that the Templar had not destroyed the Rogue Tribes, the Conclave attempted to salvage the desperate situation. They started by capturing all of the rogues.
The Conclave decided to banish the wayward Tribes from Aiur forever. The Templar under Adun were sworn to silence as the Rogues were loaded onto an ancient, but functional xel'naga ship. However, Adun's presence prompted Kortanul to psychically attack the rogues, who responded in kind. Adun feared the Rogues would accidentally create another psionic storm. He created a blue mist with a combination of Khala and strange energies, which covered and protected the rogues. However, the power caused Adun to burn out like a star. Nothing was left of his body.
Believing Adun's death was caused by the rogues, many members of the Conclave tried to attack them. Vetraas urged them to hurry and leave Aiur, which they did. Vetraas later passed away, due to natural causes.
Golden, Christie. StarCraft: The Dark Templar Saga #2: Shadow Hunters. Pocket Star Books, November 27, 2007. ISBN 0-7434-7126-1