Gauros is a living relic of the age in which the Protoss were the most potent force in the known galaxy. As such, he has a fierce sense of independence-one that made him less willing to submit to the will of their estranged brothers, the Dark Templar.
As a result, when the Zerg came to ravage and scour Aiur of all Protoss, Gauros, and those who were of like-mind, resolved to stay upon Aiur and harry the Zerg.
And so they did. The Zerg, in their stay on Aiur, were hindered in everything that they did, from raising their Zerg legions to political meetings between the Queen of Blades and her cerebrates. Throughout the Zerg occupation, there have been several unexplained-or, rather, unconfirmed-cerebrate deaths, and when the other cerebrates had been given leave to investigate the matter, they found little, or nothing, to suggest that there had been help from outside forces in the demise of these cerebrates.
But lately Gauros has seen the futility of it all. Those whom he kills are replaced by others, and those who joined him in his crusade are no longer the proud Protoss that they once were; for they are few and scattered. Seeing that he can no longer make a dent upon the Zerg, Gauros has attempted to help the Dark Templar, if but for a while. The appearance of Deimos has strengthened his decision.