The Thals are a race of humanoids
from the Doctor Who
universe inhabiting the planet Skaro
We first meet them in the story The Daleks where they are a peaceful race, having survived a genocidal war and chain of mutations they are devoted to farming and not fighting. They narrowly escape their ancient enemies in this story with the help of The Doctor and his companions.
Historicaly, however, the Thals are a warlike race, as shown in the story Genesis of the Daleks with them working slave labourers to death hauling radioactive matter into a huge warhead. The irony of this is that in the future they come to remember the Daleks as peacful scholars:
Temmosus: I wonder what they'll be like. How they'll be disposed towards us?
Ganatus: They are Daleks.
Temmosus: 'Yes, but we've changed over the centuries. Why shouldn't they? The once famous warrior race of Thals are now farmers.
Dyoni: But the Daleks were teachers weren't they, Temmosus.
Temmosus: Yes they were, and philosophers.
Ganatus: Perhaps they are the warriors now.
By the time of Earth's 26th century they possess interstellar travel, and the story of their destroying the Daleks in the past is a legend. We see them attempting to fight the Daleks on another world, perhaps due to a sense of responsibility over the creatures they helped create.