ThunderCats (1985)

S1E4 The Slaves of Castle Plun-Darr

The homeless Mutants devise a scheme to create their own refuge. To accomplish this, they capture a primitive species known as the Brute-Men, forcing them into servitude for their construction efforts. In response, the Thundercats set out for Castle Plunn-Darr with the aim of liberating the Brute-Men from the clutches of the Mutants.