T'iaz was an alien Dark Side Adept that served Emperor Palpatine. He was killed at Kira Fortress in 11 ABY aiding the Sith Lord in the abduction of Anakin Solo. While there he engaged in a duel with Rayf Ysanna who sliced off his hand and disarmed him.
T'iaz (left) with Darth Sidious in the Valley of the Dark Lords.
A member of a humanoid species, T'iaz was a male Dark Side Adept, serving the Galactic Emperor Palpatine, reborn in a clone body. In 11 ABY, due to treachery by the Emperor's physician, who had sabotaged the Emperor's clone body before the Emperor had taken it, Palpatine's clone body began to decay rapidly. The Emperor's other clone bodies had all been destroyed, and he could not clone new bodies of himself, since the physician had also tampered with the genetic material. Palpatine attempted to produce new bodies, using genetic samples from captured Force-sensitive Ysanna shamans from the planet Ossus, but Jedi Master Luke Skywalker foiled that plan.
At a loss as how to save his life, Palpatine embarked to the ancient Sith world of Korriban in order to consult the spirits of the ancient Sith Lords buried there. Arriving at the planet aboard his flagship, the Eclipse II, Palpatine used a Lambda-class shuttle to descend into the Valley of the Dark Lords, accompanied by T'iaz and another Dark Side Adept. As they traveled through the ancient Sith crypt, T'iaz felt the dark side power emanating from the place. The Sith spirits told Palpatine that the only way for him to survive would be to transfer his spirit inside Anakin Solo, the newborn son of Princess Leia Organa Solo. T'iaz swore that he would protect his Master when he would become a child, and would raise him until adulthood. Knowing that Anakin Solo was currently aboard the Millennium Falcon, en route to the planet Onderon, the Emperor and the Adepts returned to the Eclipse II and traveled to the Onderon system.
Rayf Ysanna defeats T'iaz.
The massive starship arrived in the system simultaneously with the Millennium Falcon. However, the Falcon was able to evade pursuit and landed planetside, although it soon left Onderon once again. Sensing that the child was not aboard the Falcon anymore, as it was piloted by the co-pilot Chewbacca and the Jedi Vima-Da-Boda, Palpatine chose not to pursue the ship. Instead, he decided to land on the surface of the planet, taking T'iaz and his physician with him. Posing as an old frail man, the Emperor was able to gain entrance inside Kira Fortress, where Organa Solo was taking refuge with her children. The Emperor incapacitated Organa Solo and the droid C-3PO. However, a pair of Jedi Knights, Rayf Ysanna and Empatojayos Brand, arrived to join in the fight, having recently arrived with Skywalker on Onderon. Palpatine blasted Brand with Force lightning, removing him from the fight. However, doing so drained his strength. With Ysanna left standing, Palpatine let T'iaz engage him in battle. However, the darksider was easily overpowered and killed.
Having regained his strength, Palpatine killed Ysanna. Skywalker and Han Solo arrived to join the fight, with Solo killing the Emperor with a blaster shot. Palpatine attempted to transfer his essence into the body of Anakin Solo, but his spirit was intercepted by Brand, who dragged him into the Netherworld of the Force.
The audio dramatization of Star Wars: Empire's End provides different information regarding T'iaz's death. In the audio drama, instead of going with Palpatine to the surface of Onderon, T'iaz remains to command the Eclipse II and dies when the vessel collides with the Galaxy Gun above Byss.