Raynor's Raiders and the Terran Dominion's Alpha Squadron were already investigating Char for the same reason. When Gantrithor arrived the terrans were already under attack by zerg boarders. The super carrier destroyed every terran ship regardless of affiliation to stem the infestation. Only the terran flagships, Hyperion and Norad III, escaped.
Gantrithor went into battle one last time at the end of the Great War. With Tassadar in command it joined a combined protoss and terran assault against the Overmind. To ensure the creature's destruction, Tassadar ordered the carrier on a collision course with the Overmind, while he channelled the energies of the Void for the killing blow.Gantrithor was pursued by mutalisks and guardians. Several mutalisks entered the interior and caused significant damage. The energies erupting from Tassadar's body were too great for the ship; the carrier burst apart, releasing a coruscating bolt that destroyed the Overmind.
While carrier designs would evolve, many sects of protoss would continue to construct carrier in the style of the Gantrithor many years later in order to honor its final sacrifice.
The Gantrithor is only controllable in "Eye of the Storm". It functions as a hero unit.