Prior to the conclusion of the great Neutron War with the Kaleds, the Thals were an aggressive, war like race. Earlier in Skaro's history they had already committed at least one act of genocide, eradicating the peaceful and advanced Dals from the face of the planet. While the cause of the Neutron War is unknown at this point, it is likely that the Thals' expansion lead them once more to Kaled borders. Rather than stop, the Thals advanced and initiated the thousand year war of attrition with their neighbours.
The majority of Thals were fair haired and tall, however this was not true of the entire population at this stage of their evolution. While they held certain morals, they were happy to use Kaled and Muto prisoners as a slave work force, keeping them in Spartan quarters between work shifts. These slaves were viewed as expendable – they were not Thals and so were not important life forms. Often, groups of slaves who had been exposed to toxic or radiological elements were left to die in their cells. Other times they were left in launch silos as missiles were fired, ensuring a quick but painful death for the slave force. Despite these harsh mannerisms, the Thals had grown tired of war and were willing to talk peace with the Kaleds in the latter days of the war. The stalemate grew tiresome and it was surely time to rebuild. By this point, unfortunately, the Kaleds had become focussed on victory and would accept little less than theeradication of the Thals from the face of Skaro.
When Davros offered the solution to penetrating the dome of the Kaleds' one remaining city, the chance was taken with relish. A quick end to the long war was within sight and grasp. Amidst the victory celebration, the first Daleks appeared and began the extermination of the small Thal population. Small groups escaped the massacre however and the race survived on Skaro's surface for many generations, eventually evolving into tall, blond and physically attractive humanoids. It was one such group of survivors who caused the explosion that sealed the Daleks within the Scientific Bunker shortly after Davros' extermination at the hands of his creations.
