The Ancient healing device, also known as Telchak's device, was a machine created by the Ancients.
The device itself is a cube composed of naquadah, with several buttons on the sides featuring several Ancient symbols. Its primary purpose is to heal, however it was keyed to interact with the much more advanced physiology of the Ancients, making it harmful to baseline humans (capable of driving them insane within hours of direct exposure). The device was also capable of reanimating dead tissue, even to the point of giving life to something that had not been alive before.
Reanimated dead humans take on a zombified appearance and personality. They immediately attack every living human they can find as was the case with Chalo and Volnek. How they were both fully capable of operating complex weaponry has yet to be explained. To fully kill both, they had to be blown to bits, by grenades or C-4. Otherwise they would be able to absorb a large amount of firepower until finally downed, only to rise again after a few minutes.
In the case of the Kull warriors, the host body was grown from inert tissue and then given life by this device. This process would normally result in the zombified human as described above. To compensate this effect the bodies were implanted with a live, blank, Goa'uld symbiote. This resulted in a mindless, zombie-like body controlled by a symbiote whose personality was created as desired by Anubis. (SG1: "Evolution, Part 1", "Evolution, Part 2")
Long after the Ancients left for Pegasus, a Goa'uld named Telchak discovered the device and used it to create the first sarcophagus. Anubis went to war with Telchak over the device, and, though he was victorious, Telchak hid the device on Earth, preventing Anubis from using it. After his ascension Anubis used his newfound knowledge of the workings of the device to create the Kull warriors. Fortunately, the SGC was able to locate the original device on Earth and handed it over to the Tok'ra to help develop the first Kull disruptor which proved to be a benefit against the Kull warriors. (SG1: "Evolution, Part 1", "Evolution, Part 2", "Death Knell")
The Ori also used something very similar to this device when a Prior "cursed" Volnek into a mad, undead creature that murdered the entire population of the Sodan. Teal'c and Cameron Mitchell were forced to destroy Volnek's body entirely using claymores, to prevent him from resurrecting. (SG1: " Arthur's Mantle") Similarly the Honduran terrorist had to be blown to bits after he was zombified by the device. (SG1: "Evolution, Part 1", "Evolution, Part 2")
While trapped on the planet Kinahhi, SG-1, minus Major Samantha Carter, discovered that the Arxanti, descendants of the Ancients, had an Ancient healing device. It kept them alive in the harsh climate of their ruined city and was shielded to prevent the negative effects from escaping. The Arxanti later planned to use the healing device to reverse the damage the sheh-fet had done to the Outcast, horribly mutated human beings. (SG1: "The Cost of Honor")