The following section contains information from StarCraft: Retribution.
The Executor was a templar under the command of Judicator Kizrath, tasked with securing the legendary Argus Stone from the planet of Aridas. Their first target was a series of ruins being investigated by terran teams and defended by the Aridas Colonial Militia. The Executor engaged the militia and secured the ruins, but discovered that it was a conduit to the main ruins across the river. The Executor then ordered the Protoss Crusaders to attack the militia's line across the river, and they were successful at breaking into the ruins.
Soon after, the Zerg Crusaders arrived in search of the Argus Stone, and began attacking the local militia. Judicator Kizrath gave the Executor a choice; either send a force into the militia's maintenance ducts to cause havoc behind their lines, or send a force to attack the zerg cerebrate in a cave nearby.
The Executor managed to slip a group of zealots into the zerg cave, but they met with heavy zerg resistance. The protoss force found a group of stranded Aridian militiamen, who agreed to help the protoss destroy the cerebrate's physical form. The two broke through the zerg lines, and the cerebrate's body was destroyed.
With the zealots behind the terran lines, a weakness was exposed in their front. In response, the terrans sent a raiding force to counterattack at a protoss research base. The Executor sent a force of Crusaders to secure the outpost, and used the forces there to push into the terran lines, destroying the Aridian support forces and science corps.
On the Trail of the Stone
Though the Executor was winning victory after victory, the Protoss Crusaders were not holding on all fronts. Part of the Crusaders' line had broken, allowing the Aridians to slip through and establish a stronghold between them and the stone. The Executor attacked the stronghold, and broke through the terran defense.
Soon it was discovered the Aridians were being reinforced by a supply platform in space, defended by Jenson's Raiders. The Executor launched an attack on the platform, and in spite of the efforts of its defenders destroyed all structures it housed.
Cut off and beaten back, the Executor struck at the last Aridian stronghold standing between the Protoss Crusaders and the xel'naga city of Taledon, where the Argus Stone was believed to be. The attack drove the terrans back into the ruins. There the Aridians established another base, but the Executor managed to outmaneuver them, defeating them and the ghost agents defending the ruins. The Protoss Crusaders destroyed the ruins, and Judicator Kizrath came into possession of the stone.
The Protoss Crusaders attempted to depart the planet, but were cut off by zerg forces and hassled by Aridian ghosts. The Executor still managed to break through the zerg hives, and reestablish contact with his escort fleet. Together, they destroyed the zerg hive structures in the area. However, the Escort Leader informed Kizrath and the Executor that the Conclave did not believe the stone to be important, and demanded they be sent to fight the zerg, stranding the Protoss Crusaders on Aridas.
Fate of the Crusade
Eventually, the Terran Dominion forces under Jenson Archimedes secured the stone from the protoss, destroying the temple they warped in from Aiur that attempted to channel the stone. The Zerg Crusaders then attacked the terrans, and in spite of the terrans and protoss coming together against the zerg, the zerg were able to overwhelm the Protoss Crusaders and secure passage off the planet. The Terran Dominion and Protoss Crusaders attempted to stop the zerg from using the Argus Stone on Char, but were unsuccessful.