Callous was a human mining colony. Its main resource was Swenyo, which was used in the production of star ships. The War Master, under the alias of Mr Orman, later used the rogue Ood population to slaughter the colonists in order to make the planet uninhabitable. His actions went unnoticed by the Time Lords as he delivered the shipment of Swenyo to Narvin. Originally, it had been Teremon's idea to wipe out the colonists. (AUDIO: Call for the Dead, Sins of the Father)