Having achieved the rank of lieutenant, Thace was subordinate to Commander Prorok, and both were present at Central Command when Voltron arrived to rescue Allura. To enable Voltron's escape, Thace attacked a pair of Galra Sentries and disabled the energy barrier surrounding Central Command, allowing the Castle of Lions to escape via wormhole. Prorok was subsequently arrested on suspicion for the crime, and Thace was promoted to commander by Zarkon and placed in charge of the investigation into the sabotage. He would find himself forced to deal with Haggar and her Druids, who also became involved in the search for the saboteur. Thace's situation became dangerous as one Druid discovered that the sentries had been taken down with a luxite blade and then revealed that Haggar had assigned him to accompany Thace.
Thace contacted the Blade of Marmora with news of his imminent discovery, but during one communique forgot the encrypted microchip that he used to transmit information. Upon returning to retrieve it he was apprehended by the Druids, who soon subjected him to excruciating interrogation in a bid to find out what he knew. Thace managed to hold out for some time and later escaped using his luxite blade to reset Central Command's systems to enable his comrades to upload a virus, unaware that the Druids had changed the system passwords and allowed his escape. Fortunately, Voltron Paladin Keith had infiltrated the base to carry out Thace's mission after he was presumed to have been captured, and his efforts enabled Thace to trigger an overload. Thace then remained behind while Keith made his escape, and died with a smile as the overload caused an explosion that would disable the ship's systems and enable the Blade and the Paladins to attack Zarkon.
Thace was a dedicated member of the Blade of Marmora, risking his own safety in order to provide information to the Blade of Marmora and aid the Defenders of the Universe. He was also willing to sacrifice himself for the sake of his mission and others.
Like all Blades Thace was a skilled combatant with his luxite Blade, and possessed great physical hardiness that enabled him to endure grueling torture. His mental discipline was also such that he was able to remain calm when faced by Haggar, and hide his true intentions despite Haggar's claim that she could detect any lie.