Having rescued Zeratul and his dark templar on Char, Tassadar and Executor Artanis returned to Aiur with their new allies. Upon their arrival, they were contacted by Praetor Fenix, who had been revived as a dragoon after his fall at Antioch. Fenix informed the two that the Conclave had branded them traitors for defying the Conclave's orders and associating with the dark templar. He further revealed that the Conclave intended to arrest Tassadar and kill the dark templar. Knowing that the dark templar were the only hope of defeating the zerg, Tassadar, Artanis, and Fenix resolved to protect the dark templar at all costs, even if they had to fight their own people.
Standing against the Conclave
Shortly after landing on Aiur, Tassadar and his followers came under attack from Judicator Aldaris and his troops. Aldaris demanded they surrender themselves to the Conclave immediately. They refused and retreated to Fenix's base, where they regrouped and repelled the Conclave troops. Tassadar's followers then launched a counterattack, fighting their way through the Conclave's defenses and destroying the Nexus that served as the Heart of the Conclave. Sickened by the sight of the protoss slaughtering each other, Tassadar surrendered himself to the Conclave. Artanis, Fenix and the rest of his followers eluded capture, while Zeratul and the Dark Templar disappeared. 
With the dark templar missing, Fenix convinced Artanis that they had to rescue Tassadar before the Conclave could execute him. Aided by James Raynor, whom Tassadar had befriend on Char, Tassadar's followers launched a rescue mission and freed Tassadar from his imprisonment. Aldaris and his troops appeared and surrounded the rebels, only to be surrounded in turn by Zeratul and the other dark templar. Zeratul forced the Aldaris to withdraw, and the rebels went free.
Defeating the Overmind
Having escaped the Conclave, Tassadar and his followers enacted their plan to defeat the Overmind. As part of this plan, Artanis, Fenix and Zeratul set out to destroy two cerebrates in order to weaken the Overmind's defenses. Fenix engaged the cerebrates' forces, enabling Zeratul to infiltrate the hive clusters and slay the cerebrates. 
With the Overmind's defenses breached, Tassadar's followers, now allied with Raynor's Raiders, launched their final assault on the Overmind itself. As the allied forces took up positions around the Overmind, they were contacted by Aldaris, who, having witnessed the destruction of the cerebrates, admitted that he and the Conclave had been wrong.
Tassadar's followers fought past the Overmind's defenders and attacked the Overmind itself, destroying its armored shell. By then, however, the allied forces themselves had suffered considerable casualties. In a final bid, Tassadar put the Gantrithor on a collision course with the Overmind. As the ship hurled towards the Overmind, Tassadar channeled the dark templars' energies through the ship's hull. The energies ripped the Gantrithor apart and struck the Overmind, finally killing the creature, albeit at the cost of Tassadar's life. 
- Blizzard Entertainment. StarCraft. Vivendi Games. Mission: Homeland (in English). 1998.
- Blizzard Entertainment. StarCraft. Vivendi Games. Mission: The Trial of Tassadar (in English). 1998.
- Blizzard Entertainment. StarCraft. Vivendi Games. Mission: Shadow Hunters (in English). 1998.
- Blizzard Entertainment. StarCraft. Vivendi Games. Mission: Eye of the Storm (in English). 1998.