The xel'naga encountered it and imprisoned it using an Argus crystal and the energies of the Void, beneath a barren planet around the dying star KL-2. They refused to destroy it, as they respected all life. The Argus crystal acted as a lock on the prison.
A Moebius Foundation team, led by the mildly telepathic Dr. Morrigan, researched the xel'naga ruins found on the barren world. The Voice called to her, manipulating her into building psychic amplifiers. With these, she could use her own powers to unlock the Argus crystal.
The entity converted ("possessed") approximately half of the researchers, and the rest ended up dead. The energies released notified a Dark Templar warband half a sector away. However, the entity had not absorbed enough energy from the terrans in order to completely escape.
Course of the Battle
Azimar and his subordinate Xy'tal rushed to the scene to avenge Jarzul while the rest of the warband sealed off the area. Hassan showed surprising combat ability, seeing through the protoss cloaking and surviving several warp blade strikes while severely injuring Xy'tal and spewing a converting liquid on him. Through Hassan the Voice tried to convert Azimar but failed; Azimar eventually killed Hassan.
Azimar learned much about the entity from the encounter. He believed the warband should call upon the Council for assistance, but Xy'tal convinced him it would take too long. Accepting Xy'tal's counsel, Azimar led the team into the xel'naga ruins. As they fought and killed the converted researchers, the Voice converted Xy'tal.
In the center of the structure, only Dr. Morrigan remained. Speaking through her, the Voice revealed that Xy'tal had been converted. Xy'tal and Azimar fought a duel; Xy'tal cut off Azimar's hand and burned a hole in him with his scythe before breaking free of the Voice's control. The outraged Voice attempted to burn him with black flames, to no avail.
The entity emerged from beneath the ground, attacking the Dark Templar. Xy'tal, seeking redemption, unleashed the energy in the Argus crystal as the rest of the Dark Templar fled. The resulting explosion altered space-time itself, destroying the planet and turning it into an asteroid field.
Afterward a protoss fleet arrived to investigate further. They were unable to detect any trace of the entity, but it was able to contact Azimar and taunt him.
The protoss fleet arrived and searched for the entity, finding no sign. However, the entity was still alive, taunting Azimar with the image of Xy'tal...