The Wheel of Pain was a large grain mill that was powered by slaves. Their hands were shackled to the posts of the mill and they would continuously rotate the mill throughout the day. They were only freed from the wheel once they were bought, or once they gave up and died from the physical demand of the mill.
Conan was brought to the Wheel of Pain with the other boys from his village that were captured by Thulsa Doom's snake cult after they raided the settlement. After contributing nearly two decades, Conan was the last slave left still contributing labor to the Wheel of Pain, and he was soon bought by a large warrior named Red Hair. With no one left to operate the mill, it was shut down shortly after.