The Fleshsmiths were a race from legends. They created bodies for their clients. The Seventh Doctor noted they had a reputation as "grave robbers and body snatchers" and were responsible for the disappearance of thousands of spaceships every year - their flesh banks contained captive humans, Draconians, Ice Warriors, Ogrons and even Daleks.
The Fleshsmiths had the technology to create any kind of body, no matter how complex the biology. They were able to fully recreate a Time Lord body, including regeneration capabilities. They had pioneered highly advanced surgical techniques and could transplant body parts with ease, presumably having overcome the problems of tissue rejection. They also used cybernetic implants to control and augment their servants. They could clone humanoids. They could surgically excise memories by altering neural pathways, although this process was inefficient and the memories might resurface, interfering with their control. (PROSE: Prime Time)
The Fleshsmiths were once a beautiful, highly civilised race of great poets and builders, but the formation of the Brago nebula laid waste to Scrantek and they became sterile. The corrosive nature of the Nebula eroded their bodies. They began using transplant surgery to replace damaged body parts. Eventually, their supplies of spare parts on Scrantek were exhausted. They began to kidnap aliens. Any captive too weak or infirm for use in surgery was used to test biological weapons or as food.
The Master hired the Fleshsmiths to create a new body for him. His body had been infected by the Cheetah Virus and was dying. The Fleshsmiths were stopped by the Seventh Doctor, who disabled their ship and ejected the new body for the Master into space. (PROSE: Prime Time)