As leader of the Fire Caste in the Kaurava System, Shas'O Or'es'Ka is less merciful than other Tau, implying that he doesn't serve the Greater Good or possibly because of the tactics that he employs, the Great Strength, Great Strike tactics. Or'es'Ka's base is on Nan-Yanoi, a heavily fortified secret mood base from which he launches his offensive to gain control of the Kaurava System and colonise it for the Tau Empire.
On Nan-Yanoi the Tau have constructed the massive Ar'Ka cannon that they use to soften up enemy forces before they assault them, which gives the Tau a distinct advantage when attacking.
Much like his predecessor on Kronus, Shas'O O'Kais, Or'es'Ka's battle suit features some of the same weaponry and upgrades.
Several races annihilate, enslave and torture the Tau when they're defeated, such as the Necrons, Chaos and Dark Eldar, while if the Tau are defeated by the Sisters of Battle the Cannoness Selena Agna has the skull of Or'es'Ka, along with that of the Ethereal Aun'Ro'Yr, sacrificed to the Emperor to show their devotion and as testaments of their faith.
If Or'es'Ka succeeds in taking the Kaurava System however, the Warp Storm around Kaurava IV disappears and the Kaurava System becomes an extention of the Tau Empire, another colony to be built up, although Or'es'Ka leaves this to the Ethereal Aun'Ro'Yr.