A Vorlax Regeneration Drone was a type of robot used to supply replacement bodies for soldiers who were terminally wounded in battle. They were used on the planet Grakktar in the 47th century.
History
One of these was sent back in time to 2011 on Earth by the godlike being Chiyoko. (COMIC: The Child of Time) Upon arrival, it activated its "camouflage protocol", disguising itself as a nurse called "Sister Frost" at the Hawkshaw Manor Nursing Home; there, it continued its work, creating a massive lair to build more clones for residents who were close to death.
The Eleventh Doctor and Amy soon arrived and investigated the home, with Amy getting a job as a nurse there. They were alerted by faceless children haunting residents who died shortly after, as well as a broom cupboard and children on the grounds, neither of which anybody else could see.
Upon entering the broom cupboard, they discovered the drone's lair. The Doctor prepared to send it to an uninhabited garden world, but Amy convinced him it was harming no-one and so he spared it. It then made clones for all the residents and they were all taken to an alien world. (COMIC: Do Not Go Gentle Into That Good Night) Later, again in the guise of Sister Frost, she gathered all the children in for tea. (COMIC: The Child of Time)
Technology
The Vorlax Regeneration Drone had some powerful alien technology at its disposal. The most notable of these was its aforementioned ability to create replacement bodies for those about to die. It is unknown what they looked like back where the drone came from, but at the home, they appeared as faceless children. In residents' final days the children started appearing to them at night, and upon death, they absorbed the person's consciousness, morphing into a version of that person as a child.
Other abilities included a chameleon protocol, which the drone in 2011 used to appear as "Sister Frost". It was also able to create perception filters, using this to disguise the entrance to its lair and the children it created, and it was mentioned that the drone could teleport (though the "Frost" drone's teleport drive had been damaged in a battle). (COMIC: Do Not Go Gentle Into That Good Night)