In a parallel universe, Skaro was the home planet of that universe's Daleks and Thals.
The Doctor and Alistair visited Skaro at a time when the Daleks kept the Thals prisoner as a means of protection against Davros and the Quatch. Typically the Daleks kept the Thals under tight control though compared to their previous invasions - there were regular patrols and any attempts at resistance were immediately suppressed while the Thals were given identifications. After some travels with the Doctor, Alistair chose to remain on Skaro to help the Daleks and the Thals move forward from the Quatch invasion. (AUDIO: Masters of War)