Hereafter was a planet colonised by humans. After twenty-seven generations, the humans came to call themselves Morphans. The settlements on the planet were called Aside, Beside and Seeside. Eight light years from Hereafter was Atrox 881.
The Ice Warriors landed on Hereafter and began to alter the humans' terraforming technology to make the planet more like Mars. Due to the intervention of the Eleventh Doctor, the Martians were stopped, and were relocated to Atrox 881. (PROSE: The Silent Stars Go By)